Fixed g++.dg/ext/mv16.C with -march=native.

Fixed g++.dg/ext/mv16.C with -march=native.

gcc/
	PR target/84331
	* gcc/config.gcc: Support "skylake".
	* gcc/config/i386/i386-c.c (ix86_target_macros_internal): Handle
	PROCESSOR_SKYLAKE.
	* gcc/config/i386/i386.c (m_SKYLAKE): Define.
	(processor_target_table): Add "skylake".
	(ix86_option_override_internal): Add "skylake".
	(get_builtin_code_for_version): Handle PROCESSOR_SKYLAKE,
	PROCESSOR_CANNONLAKE.
	(get_builtin_code_for_version): Fix priority for
	PROCESSOR_ICELAKE_CLIENT, PROCESSOR_ICELAKE_SERVER,
	PROCESSOR_SKYLAKE-AVX512.
	* gcc/config/i386/i386.h (processor_costs): Define TARGET_SKYLAKE.
	(processor_type): Add PROCESSOR_SKYLAKE.

gcc/testsuite/
	PR target/84331
	* gcc/testsuite/gcc.target/i386/funcspec-56.inc: Test arch=skylake.

From-SVN: r259399