Partially revert/redo 2003-10-01 change; fix -fworking-directory.

	* c-ppoutput.c (pp_dir_change):  New function.
	* c-common.h (pp_dir_change):  New declaration.
	* cpplib.h (struct cpp_options):  Remove working_directory field.
	* cppinit.c (cpp_find_main_file, cpp_push_main_file):  Merge back to
	(cpp_read_main_file):  as before 10-01.  Call _cpp_stack_file.
	Don't handle -fworking_directory here, but in c_common_post_options.
	(read_original_directory): Don't back up when done.
	Don't clear no-longer used working_directory flag.
	* cpplib.h:  Update declarations to match.
	* c-lex.c (cb_dir_change):  Move to c-opts.c.
	(init_c_lex):  Don't set dir_change callback here, since we want
	to set it even if flag_preprocess_only.
	* c-opts.c (cb_dir_change):  Function moved from c-lex.c.
	(c_common_post_options):  Set dir_change callback.
	Call pp_dir_change if approporiate.
	(finish_options):  Don't call cpp_find_main_file here.	Hence remove
	unneeded parameter and result. Do LC_RENAME for <built-in>.
	(c_common_post_options):  Call cpp_read_main_file here instead.
	(c_common_init):  Update accordingly.
	(push_command_line_include):  Don't cpp_push_main_file.
	Do LC_RENAME rather than LC_LEASE to get back to main file.
	Compared to pre-10-01 version, inline cpp_rename_to_main_file.
	(c_common_parse_file):  Call cpp_read_main_file for subsequent main
	files, but call finish_options for all files.
	* c-opts.c (sanitize_cpp_opts):  Don't set cpp_opts->working_directory.
	* fix-header.c (read_scan_file):  Call cpp_read_main_file instead of
	cpp_find_main_file + cpp_push_main_file.
	* c-lex.c (fe_file_change):  Don't set main_input_filename here.
	* opts.c (handle_options):  Only set main_input_filename first time.

From-SVN: r77303