Nothing uses these; delete them.

libcpp/ChangeLog:
	* include/line-map.h (LINEMAPS_LAST_ALLOCATED_MAP): Delete.
	(LINEMAPS_LAST_ALLOCATED_ORDINARY_MAP): Delete.
	(LINEMAPS_LAST_ALLOCATED_MACRO_MAP): Delete.

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