Make "backtrace" support -OPT options

Make "backtrace" support -OPT options

This adds support for comand options to the "backtrace" command.  We'll get:

  (gdb) bt -
  -entry-values         -hide                 -past-main
  -frame-arguments      -no-filters           -raw-frame-arguments
  -full                 -past-entry

~~~~
(gdb) help backtrace
Print backtrace of all stack frames, or innermost COUNT frames.
Usage: backtrace [OPTION]... [QUALIFIER]... [COUNT | -COUNT]

Options:
  -entry-values no|only|preferred|if-needed|both|compact|default
    Set printing of function arguments at function entry
    GDB can sometimes determine the values of function arguments at entry,
    in addition to their current values.  This option tells GDB whether
    to print the current value, the value at entry (marked as val@entry),
    or both.  Note that one or both of these values may be <optimized out>.

  -frame-arguments all|scalars|none
    Set printing of non-scalar frame arguments

  -raw-frame-arguments [on|off]
    Set whether to print frame arguments in raw form.
    If set, frame arguments are printed in raw form, bypassing any
    pretty-printers for that value.

  -past-main [on|off]
    Set whether backtraces should continue past "main".
    Normally the caller of "main" is not of interest, so GDB will terminate
    the backtrace at "main".  Set this if you need to see the rest
    of the stack trace.

  -past-entry [on|off]
    Set whether backtraces should continue past the entry point of a program.
    Normally there are no callers beyond the entry point of a program, so GDB
    will terminate the backtrace there.  Set this if you need to see
    the rest of the stack trace.

  -full
    Print values of local variables.

  -no-filters
    Prohibit frame filters from executing on a backtrace.

  -hide
    Causes Python frame filter elided frames to not be printed.

For backward compatibility, the following qualifiers are supported:

   full       - same as -full option.
   no-filters - same as -no-filters option.
   hide       - same as -hide.

With a negative COUNT, print outermost -COUNT frames.
~~~~

Implementation wise, this:

- Moves relevant options/settings globals to structures.
- Tweaks a number of functions to pass down references to such structures.
- Adds option_def structures describing the options/settings.
- Makes backtrace_command parse the options, with gdb::option::process_options.
- Tweaks "backtrace"'s help to describe the new options.
- Adds testcases.

Note that backtrace is a PROCESS_OPTIONS_UNKNOWN_IS_OPERAND command,
because of the "-COUNT" argument.

The COUNT/-COUNT argument is currently parsed as an expression.  I
considered whether it would be prudent here to require "--", but
concluded that the risk of causing a significant breakage here is much
lower compared to "print", since printing the expression is not the
whole point of the "backtrace" command.  Seems OK to me to require
typing "backtrace -past-main -- -p" if the user truly wants to refer
to the negative of a backtrace count stored in an inferior variable
called "p".

gdb/ChangeLog:
2019-06-13  Pedro Alves  <palves@redhat.com>

	* frame.c: Include "cli/cli-option.h.
	(user_set_backtrace_options): New.
	(backtrace_past_main, backtrace_past_entry, backtrace_limit):
	Delete.
	(get_prev_frame): Adjust.
	(boolean_option_def, uinteger_option_def)
	(set_backtrace_option_defs): New.
	(_initialize_frame): Adjust and use
	gdb::option::add_setshow_cmds_for_options to install "set
	backtrace past-main" and "set backtrace past-entry".
	* frame.h: Include "cli/cli-option.h".
	(struct frame_print_options): Forward declare.
	(print_frame_arguments_all, print_frame_arguments_scalars)
	(print_frame_arguments_none): Declare.
	(print_entry_values): Delete declaration.
	(struct frame_print_options, user_frame_print_options): New.
	(struct set_backtrace_options): New.
	(set_backtrace_option_defs, user_set_backtrace_options): Declare.
	* mi/mi-cmd-stack.c (mi_cmd_stack_list_frames)
	(mi_cmd_stack_list_locals, mi_cmd_stack_list_args)
	(mi_cmd_stack_list_variables): Pass down USER_FRAME_PRINT_OPTIONS.
	(list_args_or_locals): Add frame_print_options parameter.
	(mi_cmd_stack_info_frame): Pass down USER_FRAME_PRINT_OPTIONS.
	* python/py-framefilter.c (enumerate_args): Pass down
	USER_FRAME_PRINT_OPTIONS.
	* stack.c: Include "cli/cli-option.h".
	(print_frame_arguments_all, print_frame_arguments_scalars)
	(print_frame_arguments_none): Declare.
	(print_raw_frame_arguments, print_entry_values): Delete.
	(user_frame_print_options): New.
	(boolean_option_def, enum_option_def, frame_print_option_defs):
	New.
	(struct backtrace_cmd_options): New.
	(bt_flag_option_def): New.
	(backtrace_command_option_defs): New.
	(print_stack_frame): Pass down USER_FRAME_PRINT_OPTIONS.
	(print_frame_arg, read_frame_arg, print_frame_args)
	(print_frame_info, print_frame): Add frame_print_options parameter
	and use it.
	(info_frame_command_core): Pass down USER_FRAME_PRINT_OPTIONS.
	(backtrace_command_1): Add frame_print_options and
	backtrace_cmd_options parameters and use them.
	(make_backtrace_options_def_group): New.
	(backtrace_command): Process command options with
	gdb::option::process_options.
	(backtrace_command_completer): New.
	(_initialize_stack): Extend "backtrace"'s help to mention
	supported options.  Install completer for "backtrace".
	Install some settings commands with add_setshow_cmds_for_options.

gdb/testsuite/ChangeLog:
2019-06-13  Pedro Alves  <palves@redhat.com>

	* gdb.base/options.exp (test-backtrace): New.
	(top level): Call it.