Add output styles to gdb

Add output styles to gdb

This adds some output styling to the CLI.

A style is currently a foreground color, a background color, and an
intensity (dim or bold).  (This list could be expanded depending on
terminal capabilities.)

A style can be applied while printing.  For ui-out, this is done by
passing the style constant as an argument.  For low-level cases,
fprintf_styled and fputs_styled are provided.

Users can control the style via a number of new set/show commands.  In
the interest of not typing many nearly-identical documentation
strings, I automated this.  On the down side, this is not very
i18n-friendly.

I've chose some default colors to use.  I think it would be good to
enable this by default, so that when users start the new gdb, they
will see the new feature.

Stylizing is done if TERM is set and is not "dumb".  This could be
improved when the TUI is available by using the curses has_colors
call.  That is, the lowest layer could call this without committing to
using curses everywhere; see my other patch for TUI colorizing.

I considered adding a new "set_style" method to ui_file.  However,
because the implementation had to interact with the pager code, I
didn't take this approach.  But, one idea might be to put the isatty
check there and then have it defer to the lower layers.

gdb/ChangeLog
2018-12-28  Tom Tromey  <tom@tromey.com>

	* utils.h (set_output_style, fprintf_styled)
	(fputs_styled): Declare.
	* utils.c (applied_style, desired_style): New globals.
	(emit_style_escape, set_output_style): New function.
	(prompt_for_continue): Emit style escapes.
	(fputs_maybe_filtered): Likewise.
	(fputs_styled, fprintf_styled): New functions.
	* ui-out.h (enum class ui_out_style_kind): New.
	(class ui_out) <field_string, field_stream, do_field_string>: Add
	style parameter.
	* ui-out.c (ui_out::field_stream, ui_out::field_string): Add style
	parameter.
	* tui/tui-out.h (class tui_ui_out) <do_field_string>: Add style
	parameter.
	* tui/tui-out.c (tui_ui_out::do_field_string): Add style
	parameter.
	(tui_ui_out::do_field_string): Update.
	* tracepoint.c (print_one_static_tracepoint_marker): Style
	output.
	* stack.c (print_frame_info, print_frame): Style output.
	* source.c (print_source_lines_base): Style output.
	* skip.c (info_skip_command): Style output.
	* record-btrace.c (btrace_call_history_src_line): Style output.
	(btrace_call_history): Likewise.
	* python/py-framefilter.c (py_print_frame): Style output.
	* mi/mi-out.h (class mi_ui_out) <do_field_string>: Add style
	parameter.
	* mi/mi-out.c (mi_ui_out::do_table_header)
	(mi_ui_out::do_field_int): Update.
	(mi_ui_out::do_field_string): Update.
	* disasm.c (gdb_pretty_print_disassembler::pretty_print_insn):
	Style output.
	* cli/cli-style.h: New file.
	* cli/cli-style.c: New file.
	* cli-out.h (class cli_ui_out) <do_field_string>: Add style
	parameter.
	* cli-out.c (cli_ui_out::do_table_header)
	(cli_ui_out::do_field_int, cli_ui_out::do_field_skip): Update.
	(cli_ui_out::do_field_string): Add style parameter.  Style the
	output.
	* breakpoint.c (print_breakpoint_location): Style output.
	(update_static_tracepoint): Likewise.
	* Makefile.in (SUBDIR_CLI_SRCS): Add cli-style.c.
	(HFILES_NO_SRCDIR): Add cli-style.h.

gdb/testsuite/ChangeLog
2018-12-28  Tom Tromey  <tom@tromey.com>

	* gdb.base/style.exp: New file.
	* gdb.base/style.c: New file.