Support location tracking for built-in macro tokens

Support location tracking for built-in macro tokens

When a built-in macro is expanded, the location of the token in the
epansion list is the location of the expansion point of the built-in
macro.

This patch creates a virtual location for that token instead,
effectively tracking locations of tokens resulting from built-in macro
tokens.

libcpp/
	* include/line-map.h (line_maps::builtin_location): New data
	member.
	(line_map_init): Add a new parameter to initialize the new
	line_maps::builtin_location data member.
	* line-map.c (linemap_init): Initialize the
	line_maps::builtin_location data member.
	* macro.c (builtin_macro): Create a macro map and track the token
	resulting from the expansion of a built-in macro.
gcc/
	* input.h (is_location_from_builtin_token): New function
	declaration.
	* input.c (is_location_from_builtin_token): New function
	definition.
	* toplev.c (general_init): Tell libcpp what the pre-defined
	spelling location for built-in tokens is.

Signed-off-by: Dodji Seketeli <dodji@redhat.com>
From-SVN: r212637