* config.host (<i[34567]86-*-*, x86_64-*-*>): Set
	host_extra_gcc_objs and host_xmake_file.
	(<*-*-linux*>): Don't overwrite host_xmake_file.
	* gcc.c (static_spec_functions): Add EXTRA_SPEC_FUNCTIONS.
	* config/i386/i386.h (EXTRA_SPEC_FUNCTIONS): Define.
	(host_detect_local_cpu): Declare.
	(CC1_CPU_SPEC): Add -march=native and -mtune=native cases.
	* config/i386/i386.c (override_options): Handle -mtune=native
	as -mtune=generic.
	* config/i386/x-i386: New file.
	* config/i386/driver-i386.c: New file.
	* doc/invoke.texi (<i386 and x86-64 Options>): Describe
	cpu-type "native".

From-SVN: r113655