libcpp: eliminate MACRO_MAP_EXPANSION_POINT_LOCATION

This patch eliminates the function "MACRO_MAP_EXPANSION_POINT_LOCATION"
(which hasn't been a macro since r6-739-g0501dbd932a7e9) in favor of
a new line_map_macro::get_expansion_point_location accessor.

No functional change intended.

gcc/c-family/ChangeLog:
	* c-warn.cc (warn_for_multistatement_macros): Update for removal
	of MACRO_MAP_EXPANSION_POINT_LOCATION.

gcc/cp/ChangeLog:
	* module.cc (ordinary_loc_of): Update for removal of
	MACRO_MAP_EXPANSION_POINT_LOCATION.
	(module_state::note_location): Update for renaming of field.
	(module_state::write_macro_maps): Likewise.

gcc/ChangeLog:
	* input.cc (dump_location_info): Update for removal of
	MACRO_MAP_EXPANSION_POINT_LOCATION.
	* tree-diagnostic.cc (maybe_unwind_expanded_macro_loc):
	Likewise.

libcpp/ChangeLog:
	* include/line-map.h
	(line_map_macro::get_expansion_point_location): New accessor.
	(line_map_macro::expansion): Rename field to...
	(line_map_macro::mexpansion): Rename field to...
	(MACRO_MAP_EXPANSION_POINT_LOCATION): Delete this function.
	* line-map.cc (linemap_enter_macro): Update for renaming of field.
	(linemap_macro_map_loc_to_exp_point): Update for removal of
	MACRO_MAP_EXPANSION_POINT_LOCATION.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>