c++: modules and DECL_REPLACEABLE_P

We need to remember that the ::operator new is replaceable to avoid a bogus
error about __builtin_operator_new finding a non-replaceable function.

This affected __get_temporary_buffer in stl_tempbuf.h.

gcc/cp/ChangeLog:

	* module.cc (trees_out::core_bools): Write replaceable_operator.
	(trees_in::core_bools): Read it.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/operator-2_a.C: New test.
	* g++.dg/modules/operator-2_b.C: New test.