c: fmv: Prevent FMV being combined with other cloning/renaming extensions.

c: fmv: Prevent FMV being combined with other cloning/renaming extensions.

This patch adds exclusions and diagnostics to prevent function multi-versioning
being used with omp simd pragmas and renaming extensions.

This behaviour is forbidden by the ACLE as the expected behaviour is not clear.

gcc/c-family/ChangeLog:

	* c-attribs.cc (attr_target_clones_exclusions): Add simd and omp
	exclusions.
	(attr_target_version_exclusions): New definition with simd and omp
	exclusions.
	(attr_omp_declare_simd_exclusions): New definition with target_version
	and clones exclusions.
	(attr_simd_exclusions): Ditto.
	(c_common_gnu_attributes): Add new target_version, simd, and omp
	declare simd variables.

gcc/c/ChangeLog:

	* c-decl.cc (maybe_mark_function_versioned): Add diagnostic.
	* c-parser.cc (c_finish_omp_declare_simd): Add diagnostic.

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/mv-error11.c: New test.
	* gcc.target/aarch64/mv-error12.c: New test.