* cppfiles.c (stack_include_file): line-map.c now handles include
	depth.
	(handle_missing_handler): Similarly.
	(_cpp_execute_include): Similarly.
	(_cpp_pop_file_buffer): Similarly.
	* cpphash.h (struct cpp_reader): Remove system_include_depth,
	buffer_stack_depth and include_depth.
	* cpplib.c (do_include_common): line-map.c now handles include depth.
	(cpp_push_buffer): Similarly.
	(_cpp_pop_buffer): Similarly.
	* cppmacro.c (builtin_macro): Update.
	* line-map.c (init_line_maps): Set depth.
	(add_line_map): Increment "used" earlier.  Update and use the
	include depth.
	(trace_include): Use the include depth.
	* line-map.h (struct line_maps): New member depth.

From-SVN: r45085