Allow matching Intel MIC in OpenMP 'declare variant'

Allow matching Intel MIC in OpenMP 'declare variant'

..., and use that to improve XFAILing for Intel MIC offloading execution
instead of compilation in 'libgomp.c-c++-common/target-45.c',
'libgomp.fortran/target10.f90'.

	gcc/
	* config/i386/i386-options.c (ix86_omp_device_kind_arch_isa)
	<omp_device_arch> [ACCEL_COMPILER]: Match "intel_mic".
	* config/i386/t-omp-device (omp-device-properties-i386) <arch>:
	Add "intel_mic".
	libgomp/
	* testsuite/lib/libgomp.exp
	(check_effective_target_offload_target_intelmic): Remove 'proc'.
	(check_effective_target_offload_device_intel_mic): New 'proc'.
	* testsuite/libgomp.c-c++-common/on_device_arch.h
	(device_arch_intel_mic, on_device_arch_intel_mic): New.
	* testsuite/libgomp.c-c++-common/target-45.c: Use that for
	'dg-xfail-run-if'.
	* testsuite/libgomp.fortran/target10.f90: Likewise.