re PR fortran/25324 (Wrong DW_TAG_compile_unit generated when compiling preprocessed fortran code)

	PR fortran/25324
	* Make-lang.in (fortran/scanner.o): Depend on toplev.h.
	* lang.opt (fpreprocessed): New option.
	* scanner.c: Include toplev.h.
	(gfc_src_file, gfc_src_preprocessor_lines): New variables.
	(preprocessor_line): Unescape filename if there were any
	backslashes.
	(load_file): If initial and gfc_src_file is not NULL,
	use it rather than opening the file.  If gfc_src_preprocessor_lines
	has non-NULL elements, pass it to preprocessor_line.
	(unescape_filename, gfc_read_orig_filename): New functions.
	* gfortran.h (gfc_option_t): Add flag_preprocessed.
	(gfc_read_orig_filename): New prototype.
	* options.c (gfc_init_options): Clear flag_preprocessed.
	(gfc_post_options): If flag_preprocessed, call
	gfc_read_orig_filename.
	(gfc_handle_option): Handle OPT_fpreprocessed.
	* lang-specs.h: Pass -fpreprocessed to f951 if preprocessing
	sources.

From-SVN: r110304