Introduce gdb-specific %p format suffixes

Introduce gdb-specific %p format suffixes

This introduces a few gdb-specific %p format suffixes.  This is useful
for emitting gdb-specific output in an ergonomic way.  It also yields
code that is more i18n-friendly.

The comment before ui_out::message explains the details.

Note that the tests had to change a little.  When using one of the gdb
printf functions with styling, there can be spurious style changes
emitted to the output.  This did not seem worthwhile to fix, as the
low-level output functions are rather spaghetti-ish already, and I
didn't want to make them even worse.

This change also necessitated adding support for "*" as precision and
width in format_pieces.  These are used in various spots in gdb, and
it seemed better to me to implement them than to remove the uses.

gdb/ChangeLog
2019-10-01  Pedro Alves  <palves@redhat.com>
	    Tom Tromey  <tom@tromey.com>

	* unittests/format_pieces-selftests.c: Add gdb_format parameter.
	(test_gdb_formats): New function.
	(run_tests): Call it.
	(test_format_specifier): Update.
	* utils.h (fputs_filtered): Update comment.
	(vfprintf_styled, vfprintf_styled_no_gdbfmt)
	(fputs_styled_unfiltered): Declare.
	* utils.c (fputs_styled_unfiltered): New function.
	(vfprintf_maybe_filtered): Add gdbfmt parameter.
	(vfprintf_filtered): Update.
	(vfprintf_unfiltered, vprintf_filtered): Update.
	(vfprintf_styled, vfprintf_styled_no_gdbfmt): New functions.
	* ui-out.h (enum ui_out_flag) <unfiltered_output,
	disallow_ui_out_field>: New constants.
	(enum class field_kind): New.
	(struct base_field_s, struct signed_field_s): New.
	(signed_field): New function.
	(struct string_field_s): New.
	(string_field): New function.
	(struct styled_string_s): New.
	(styled_string): New function.
	(class ui_out) <message>: Add comment.
	<vmessage, call_do_message>: New methods.
	<do_message>: Add style parameter.
	* ui-out.c (ui_out::call_do_message, ui_out::vmessage): New
	methods.
	(ui_out::message): Rewrite.
	* mi/mi-out.h (class mi_ui_out) <do_message>: Add style
	parameter.
	* mi/mi-out.c (mi_ui_out::do_message): Add style parameter.
	* gdbsupport/format.h (class format_pieces) <format_pieces>: Add
	gdb_extensions parameter.
	(class format_piece): Add parameter to constructor.
	(n_int_args): New field.
	* gdbsupport/format.c (format_pieces::format_pieces): Add
	gdb_extensions parameter.  Handle '*'.
	* cli-out.h (class cli_ui_out) <do_message>: Add style parameter.
	* cli-out.c (cli_ui_out::do_message): Add style parameter.  Call
	vfprintf_styled_no_gdbfmt.
	(cli_ui_out::do_field_string, cli_ui_out::do_spaces)
	(cli_ui_out::do_text, cli_ui_out::field_separator): Allow
	unfiltered output.
	* ui-style.h (struct ui_file_style) <ptr>: New method.

gdb/testsuite/ChangeLog
2019-10-01  Tom Tromey  <tom@tromey.com>

	* gdb.base/style.exp: Update tests.