Introduce "info breakpoints -hide-locations"

Introduce "info breakpoints -hide-locations"

This commit adds a new option to "info breakpoints",
"-hide-locations".  It's purpose is to tell GDB to skip printing
breakpoint locations, printing only the breakpoint header rows.

And then, since only code breakpoint locations print anything in the
"Address" column, "-hide-breakpoints" also disables the "Address"
column.

For example, when debugging GDB, you can use the new options to get
this:

 (top-gdb) i b -h
 Num     Type           Disp Enb What
 1       breakpoint     keep y   internal_error
 2       breakpoint     keep y   info_command
	 silent
	 return
 3       breakpoint     keep y   main
	 breakpoint already hit 1 time
 4       breakpoint     keep y   error
 (top-gdb)

instead of:

 (top-gdb) i b
 Num     Type           Disp Enb Address            What
 1       breakpoint     keep y                      internal_error
  1.1                        y   0x0000555555f81d12 in internal_error(char const*, int, char const*, ...) at /home/pedro/gdb/binutils-gdb/src/gdbsupport/errors.cc:51
 2       breakpoint     keep y                      info_command
	 silent
	 return
  2.1                        y   0x00005555557b3097 in info_command(char const*, int) at /home/pedro/gdb/binutils-gdb/src/gdb/cli/cli-cmds.c:217
 3       breakpoint     keep y                      main
	 breakpoint already hit 1 time
  3.1                        y   0x000055555564106c in main(int, char**) at /home/pedro/gdb/binutils-gdb/src/gdb/gdb.c:25
  3.2                        y   0x0000555555dba524 in selftests::string_view::capacity_1::main() at /home/pedro/gdb/binutils-gdb/src/gdb/unittests/basic_string_view/capacity/1.cc:167
  3.3                        y   0x0000555555dba943 in selftests::string_view::cons_1::main() at /home/pedro/gdb/binutils-gdb/src/gdb/unittests/basic_string_view/cons/char/1.cc:62
  3.4                        y   0x0000555555dbaa34 in selftests::string_view::cons_2::main() at /home/pedro/gdb/binutils-gdb/src/gdb/unittests/basic_string_view/cons/char/2.cc:41
  3.5                        y   0x0000555555dbaa9a in selftests::string_view::cons_3::main() at /home/pedro/gdb/binutils-gdb/src/gdb/unittests/basic_string_view/cons/char/3.cc:34
  3.6                        y   0x0000555555dbac6b in selftests::string_view::element_access_1::main() at /home/pedro/gdb/binutils-gdb/src/gdb/unittests/basic_string_view/element_access/char/1.cc:66
  3.7                        y   0x0000555555dbac83 in selftests::string_view::element_access_empty::main() at /home/pedro/gdb/binutils-gdb/src/gdb/unittests/basic_string_view/element_access/char/empty.cc:25
  3.8                        y   0x0000555555dbae91 in selftests::string_view::element_access_front_back::main()
						    at /home/pedro/gdb/binutils-gdb/src/gdb/unittests/basic_string_view/element_access/char/front_back.cc:38
  3.9                        y   0x0000555555dbb2bd in selftests::string_view::inserters_2::main() at /home/pedro/gdb/binutils-gdb/src/gdb/unittests/basic_string_view/inserters/char/2.cc:84
  3.10                       y   0x0000555555dbb429 in selftests::string_view::modifiers_remove_prefix::main()
						    at /home/pedro/gdb/binutils-gdb/src/gdb/unittests/basic_string_view/modifiers/remove_prefix/char/1.cc:58
  3.11                       y   0x0000555555dbb575 in selftests::string_view::modifiers_remove_suffix::main()
						    at /home/pedro/gdb/binutils-gdb/src/gdb/unittests/basic_string_view/modifiers/remove_suffix/char/1.cc:58
  3.12                       y   0x0000555555dbbd38 in selftests::string_view::operations_compare_1::main() at /home/pedro/gdb/binutils-gdb/src/gdb/unittests/basic_string_view/operations/compare/char/1.cc:127
  3.13                       y   0x0000555555dbbe7b in selftests::string_view::operations_compare_13650::main()
						    at /home/pedro/gdb/binutils-gdb/src/gdb/unittests/basic_string_view/operations/compare/char/13650.cc:45
  3.14                       y   0x0000555555dbbf6a in selftests::string_view::operations_copy_1::main() at /home/pedro/gdb/binutils-gdb/src/gdb/unittests/basic_string_view/operations/copy/char/1.cc:41
  3.15                       y   0x0000555555dbc03b in selftests::string_view::operations_data_1::main() at /home/pedro/gdb/binutils-gdb/src/gdb/unittests/basic_string_view/operations/data/char/1.cc:39
  3.16                       y   0x0000555555dbc5fe in selftests::string_view::operations_find_1::main() at /home/pedro/gdb/binutils-gdb/src/gdb/unittests/basic_string_view/operations/find/char/1.cc:160
  3.17                       y   0x0000555555dbcb60 in selftests::string_view::operations_find_2::main() at /home/pedro/gdb/binutils-gdb/src/gdb/unittests/basic_string_view/operations/find/char/2.cc:158
  3.18                       y   0x0000555555dbd1c1 in selftests::string_view::operations_find_3::main() at /home/pedro/gdb/binutils-gdb/src/gdb/unittests/basic_string_view/operations/find/char/3.cc:158
  3.19                       y   0x0000555555dbd26c in selftests::string_view::operations_find_4::main() at /home/pedro/gdb/binutils-gdb/src/gdb/unittests/basic_string_view/operations/find/char/4.cc:40
  3.20                       y   0x0000555555dbd83f in selftests::string_view::operations_rfind_1::main() at /home/pedro/gdb/binutils-gdb/src/gdb/unittests/basic_string_view/operations/rfind/char/1.cc:90
  3.21                       y   0x0000555555dbda98 in selftests::string_view::operations_rfind_2::main() at /home/pedro/gdb/binutils-gdb/src/gdb/unittests/basic_string_view/operations/rfind/char/2.cc:48
  3.22                       y   0x0000555555dbde4c in selftests::string_view::operations_rfind_3::main() at /home/pedro/gdb/binutils-gdb/src/gdb/unittests/basic_string_view/operations/rfind/char/3.cc:63
  3.23                       y   0x0000555555dbe189 in selftests::string_view::operations_substr_1::main() at /home/pedro/gdb/binutils-gdb/src/gdb/unittests/basic_string_view/operations/substr/char/1.cc:74
  3.24                       y   0x0000555555dbffdb in selftests::string_view::operators_2::main() at /home/pedro/gdb/binutils-gdb/src/gdb/unittests/basic_string_view/operators/char/2.cc:366
 4       breakpoint     keep y                      error
  4.1                        y   0x00005555557f5142 in gcc_c_plugin::error(char const*) const at /home/pedro/gdb/binutils-gdb/src/gdb/../include/gcc-c-fe.def:198
  4.2                        y   0x00005555557fe1f4 in gcc_cp_plugin::error(char const*) const at /home/pedro/gdb/binutils-gdb/src/gdb/../include/gcc-cp-fe.def:983
  4.3                        y   0x0000555555f81c5e in error(char const*, ...) at /home/pedro/gdb/binutils-gdb/src/gdbsupport/errors.cc:39
  4.4                        y   0x00007ffff65ee4e0 <icu_66::RBBIRuleScanner::error(UErrorCode)>
  4.5                        y   0x00007ffff685e070 <icu_66::RegexCompile::error(UErrorCode)>
  4.6                        y   0x00007ffff6cd4e86 in error at /usr/include/x86_64-linux-gnu/bits/error.h:40
  4.7                        y   0x00007ffff71c2190 in __error at error.c:274

Documentation change included.  No testsuite changes yet until there's
agreement on the previous patch.

Change-Id: Ic42ad8565e79ca67bfebb22cbb4794ea816fd08b