Fixes test subobj6.test and PR automake/160:

	Fixes test subobj6.test and PR automake/160:
	* tests/Makefile.am (XFAIL_TESTS): Removed subobj6.test.
	* compile.am (mostlyclean-compile): Added MOSTLYRMS.
	(distclean-compile): Added DISTRMS.
	* tests/subobj6.test (wish_SOURCES): Updated to reflect
	`mostlyclean' use; added test for non-subdir case.
	* automake.in (compile_clean_files): New global.
	(MOSTLY_CLEAN, DIST_CLEAN): New constants.
	(initialize_per_input): Initialize compile_clean_files.
	(handle_single_transform_list): Set compile_clean_files entries.
	(handle_compile): Handle compilation cleanups.