Add -march=ia to x86 backend

	* config.gcc: Support --with-cpu=ia.

	* config/i386/i386.c (cpu_names): Add "ia".
	(processor_alias_table): Likewise.
	(ix86_option_override_internal): Disallow -march=ia.
	* config/i386/i386.h (target_cpu_default): Add
	TARGET_CPU_DEFAULT_ia.

	* doc/invoke.texi: Document -mtune=ia.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@205719 138bc75d-0d04-0410-961f-82ee72b054a4