cpp.texi: Update documentation for -include and -imacros.

cpp.texi: Update documentation for -include and -imacros.

	* cpp.texi: Update documentation for -include and -imacros.
	* cppfiles.c (struct include_file): Remove "defined" memeber.
	(find_or_create_entry): Make a copy of the file name, and
	simplify it.
	(open_file): Update to ensure we use the simplified filename.
	(stack_include_file): Don't set search_from.
	(cpp_included): Don't simplify the path name here.
	(find_include_file): New prototype.  Call search_from to
	get the start of the "" include chain.  Don't simplify the
	filenames here.
	(_cpp_execute_include): New prototype.  Move diagnostics to
	do_include_common.  Update.
	(_cpp_pop_file_buffer): Don't set defined.
	(search_from): New prototype.  Use the preprocessor's cwd
	for files included from the command line.
	(read_name_map): Don't simplify the pathname here.
	* cpphash.h (enum include_type): New.
	(struct buffer): Delete search from.  New search_cached.
	(_cpp_execute_include): Update prototype.
	* cppinit.c (do_includes): Use _cpp_execute_include.
	* cpplib.c (do_include_common): New function.
	(do_include, do_include_next, do_import): Use it.

From-SVN: r40486