c++: Fix missing NSDMI diagnostic in C++98 [PR103347]

c++: Fix missing NSDMI diagnostic in C++98 [PR103347]

Here the problem is that we aren't detecting a NSDMI in C++98:

struct A {
  void *x = NULL;
};

because maybe_warn_cpp0x uses input_location and that happens to point
to NULL which comes from a system header.  Jakub suggested changing the
location to the '=', thereby avoiding the system header problem.  To
that end, I've added a new location_t member into cp_declarator.  This
member is used when this declarator is part of an init-declarator.  The
rest of the changes is obvious.  I've also taken the liberty of adding
loc_or_input_loc, since I want to avoid checking for UNKNOWN_LOCATION.

	PR c++/103347

gcc/cp/ChangeLog:

	* cp-tree.h (struct cp_declarator): Add a location_t member.
	(maybe_warn_cpp0x): Add a location_t parameter with a default argument.
	(loc_or_input_loc): New.
	* decl.c (grokdeclarator): Use loc_or_input_loc.  Pass init_loc down
	to maybe_warn_cpp0x.
	* error.c (maybe_warn_cpp0x): Add a location_t parameter.  Use it.
	* parser.c (make_declarator): Initialize init_loc.
	(cp_parser_member_declaration): Set init_loc.
	(cp_parser_condition): Likewise.
	(cp_parser_init_declarator): Likewise.
	(cp_parser_parameter_declaration): Likewise.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/nsdmi-warn1.C: New test.
	* g++.dg/cpp0x/nsdmi-warn1.h: New file.