selftest: introduce class auto_fix_quotes

selftest: introduce class auto_fix_quotes

This patch moves a workaround for locale differences from a
selftest in pretty-print.c to selftest.h/c to make it reusable; I need
this for a selftest in a followup patch.

gcc/ChangeLog:
	* pretty-print.c (selftest::test_pp_format): Move save and restore
	of quotes to class auto_fix_quotes, and add an instance.
	* selftest.c: Include "intl.h".
	(selftest::auto_fix_quotes::auto_fix_quotes): New ctor.
	(selftest::auto_fix_quotes::~auto_fix_quotes): New dtor.
	* selftest.h (selftest::auto_fix_quotes): New class.

From-SVN: r262317