Add styling to macro commands

Add styling to macro commands

This adds filename styling to "info macro".

gdb/ChangeLog
2019-02-17  Tom Tromey  <tom@tromey.com>

	* macrocmd.c (show_pp_source_pos): Style the file names.

gdb/testsuite/ChangeLog
2019-02-17  Tom Tromey  <tom@tromey.com>

	* gdb.base/style.exp: Use -g3 to compile when possible.  Add test
	for macro styling.
	* gdb.base/style.c (SOME_MACRO): New macro.