config.gcc (mips64el-st-linux-gnu): Use mips/st.h and mips/t-st.

config.gcc (mips64el-st-linux-gnu): Use mips/st.h and mips/t-st.

	* config.gcc (mips64el-st-linux-gnu): Use mips/st.h and mips/t-st.
	* config.host: Use driver-native.o and mips/x-native for mips*-linux*.
	* config/mips/linux.h (host_detect_local_cpu): Declare, add to
	EXTRA_SPEC_FUNCTIONS.
	(MARCH_MTUNE_NATIVE_SPECS, BASE_DRIVER_SELF_SPECS): New macros.
	(DRIVER_SELF_SPECS): Adjust.
	* config/mips/linux64.h (DRIVER_SELF_SPECS): Update.
	* config/mips/st.h, config/mips/t-st: New.
	* config/mips/driver-native.c, config/mips/x-native: New.
	* doc/invoke.texi (MIPS): Document 'native' value for -march and
	-mtune options.

Co-Authored-By: Kazu Hirata <kazu@codesourcery.com>
From-SVN: r136888