PR 10979

	PR 10979
	* common.cc (Sort_commons::operator()): Stabilize sort when both
	entries are NULL.
	(Symbol_table::do_allocate_commons_list): When allocating common
	symbols, skip a symbol which is no longer common.
	* symtab.h (Symbol::is_common): Test whether the symbol comes from
	an object before checking its type.
	* testsuite/common_test_2.c: New file.
	* testsuite/common_test_3.c: New file.
	* testsuite/Makefile.am (check_PROGRAMS): Add common_test_2.
	(common_test_2_SOURCES, common_test_2_DEPENDENCIES): Define.
	(common_test_2_LDFLAGS, common_test_2_LDADD): Define.
	(common_test_2_pic.o, common_test_2.so): New targets.
	(common_test_3_pic.o, common_test_3.so): New targets.
	* testsuite/Makefile.in: Rebuild.