[x86][patch] Add -march=cannonlake.

[Koval, Julia]

Hi, this patch adds new option -march=cannonlake. Isasets defined in: https://software.intel.com/sites/default/files/managed/c5/15/architecture-instruction-set-extensions-programming-reference.pdf

Ok for trunk?

gcc/
	* config.gcc: Add -march=cannonlake.
	* config/i386/driver-i386.c (host_detect_local_cpu): Detect cannonlake.
	* config/i386/i386-c.c (ix86_target_macros_internal): Handle cannonlake.
	* config/i386/i386.c (processor_costs): Add m_CANNONLAKE.
	(PTA_CANNONLAKE): New.
	(processor_target_table): Add cannonlake.
	(ix86_option_override_internal): Ditto.
	(fold_builtin_cpu): Ditto.
	(get_builtin_code_for_version): Handle cannonlake.
	(M_INTEL_CANNONLAKE): New.
	* config/i386/i386.h (TARGET_CANNONLAKE, PROCESSOR_CANNONLAKE): New.
	* doc/invoke.texi: Add -march=cannonlake.
gcc/testsuite/
	* gcc.target/i386/funcspec-56.inc: Handle new march.

Thanks,
Julia