Add -s option to source command.

	Add -s option to source command.
	* NEWS: Document new option.
	* cli/cli-cmds.c (find_and_open_script): Add function comment.
	Delete from_tty and cleanupp args.  Split filep arg into file and
	full_pathp.  New arg search_path.
	(source_script_from_stream): New function.
	(source_script_with_search): New function.
	(source_script): Rewrite.
	(source_command): Parse "-s" option.
	(init_cli_cmds): Add "-s" docs to source command help, and reformat.
	* python/python.c (source_python_script): Make file arg a const char *.
	Don't call fclose, leave for caller.
	* python/python.h (source_python_script): Update.

	testsuite/
	* gdb.base/source-test.gdb: New file.
	* gdb.base/source.exp: Add tests for "source -s".

	doc/
	* gdb.texinfo (Command Files): Add docs for new "source -s" option.