* cppfiles.c (stack_include_file): Don't handle -H here.
	* cppinit.c (cpp_start_read): Set include tracing after
	cpp_post_options and after stacking the main file.
	* line-map.c (trace_include): New.
	(init_line_maps, add_line_map): Update.
	* line-map.h (struct line_maps): New member trace_includes.

From-SVN: r45084