Start adding target-specific selftests

Start adding target-specific selftests

gcc/ChangeLog:
	* config/i386/i386.c: Include "selftest.h" and "selftest-rtl.h".
	(selftest::ix86_test_dumping_hard_regs): New function.
	(selftest::ix86_run_selftests): New function.
	(TARGET_RUN_TARGET_SELFTESTS): When CHECKING_P, wire this up to
	selftest::ix86_run_selftests.
	* doc/tm.texi.in (TARGET_RUN_TARGET_SELFTESTS): New.
	* doc/tm.texi: Regenerate
	* selftest-rtl.h: New file.
	* rtl-tests.c: Include "selftest-rtl.h".
	(selftest::assert_rtl_dump_eq): Make non-static.
	(ASSERT_RTL_DUMP_EQ): Move to selftest-rtl.h.
	(selftest::test_dumping_regs): Update comment.
	* selftest-run-tests.c: Include "target.h".
	(selftest::run_tests): If non-NULL, call
	targetm.run_target_selftests.
	* target.def (run_target_selftests): New hook.

From-SVN: r241851