* buildsym.c (patch_subfile_names): Use set_last_source_file.

	* buildsym.c (patch_subfile_names): Use set_last_source_file.
	(start_symtab): Make 'name' and 'dirname' const.  Use
	set_last_source_file.
	(restart_symtab, reset_symtab_globals): Use set_last_source_file.
	(last_source_file): Define.  Now static.
	(set_last_source_file, get_last_source_file): New functions.
	* buildsym.h (last_source_file): Don't declare.
	(start_symtab): Update.
	(set_last_source_file, get_last_source_file): Declare.
	* coffread.c (complete_symtab): Use set_last_source_file.
	(coff_end_symtab): Likewise.
	(coff_symtab_read): Use set_last_source_file, get_last_source_file.
	* dbxread.c (read_dbx_symtab, read_ofile_symtab): Use
	set_last_source_file.
	(process_one_symbol): Use get_last_source_file.
	* mdebugread.c (parse_partial_symbols): Use set_last_source_file.
	(psymtab_to_symtab_1): Use get_last_source_file.
	* xcoffread.c (process_linenos): Use get_last_source_file.
	(complete_symtab): Use set_last_source_file.
	(read_xcoff_symtab): Use set_last_source_file, get_last_source_file.
	(scan_xcoff_symtab): Use set_last_source_file.