c: Synthesize nonnull attribute for parameters declared with static [PR110815]

c: Synthesize nonnull attribute for parameters declared with static [PR110815]

Parameters declared with `static` are nonnull. We synthesize
an artifical nonnull attribute for such parameters to get the
same warnings and optimizations.

Bootstrapped and regression tested on x86.

	PR c/110815
	PR c/112428

gcc/c-family:
	* c-attribs.cc (build_attr_access_from_parms): Synthesize
	nonnull attribute for parameters declared with `static`.

gcc:
	* gimple-ssa-warn-access.cc (pass_waccess::maybe_check_access_sizes):
	remove warning for parameters declared with `static`.

gcc/testsuite:
	* gcc.dg/Wnonnull-8.c: Adapt test.
	* gcc.dg/Wnonnull-9.c: New test.