driver: fix validate_switches logic

driver: fix validate_switches logic

Under the old logic for validate_switches, once suffix or starred got set,
they stayed set for all later switches found in the spec.  So for e.g.

%{g*:%{%:debug-level-gt(0):

Once we see g*, starred is set.  Then we see %:, and it sees that as a
zero-length switch, which because starred is still set, matches any and all
command-line options.  So targets that use such a spec accept all options in
the driver, while ones that don't reject some, such as the recent
-nostdlib++.

This patch fixes the inconsistency, so all targets would complain about
-nostdlib++, and then sets SKIPOPT for it so they don't.

gcc/ChangeLog:

	* gcc.cc (validate_switches): Reset suffix/starred on loop.

gcc/cp/ChangeLog:

	* g++spec.cc (lang_specific_driver): Set SKIPOPT for nostdlib++.