Start adding selftests for print_rtx

Start adding selftests for print_rtx

gcc/ChangeLog:
	* print-rtl-function.c (flag_compact): Move extern decl to...
	* print-rtl.h (flag_compact): ...here.
	* rtl-tests.c (selftests::assert_rtl_dump_eq): New function.
	(ASSERT_RTL_DUMP_EQ): New macro.
	(selftest::test_dumping_regs): New function.
	(selftest::test_dumping_insns): New function.
	(selftest::test_uncond_jump): Add uses of ASSERT_RTL_DUMP_EQ on
	the insns.
	(selftest::rtl_tests_c_tests): Call the new test functions.

From-SVN: r241405