* source.c (get_current_or_default_source_symtab_and_line): Remove

	* source.c (get_current_or_default_source_symtab_and_line): Remove
	function.
	(set_default_source_symtab_and_line): New function. Attempts to
	determine a source file to list lines from if one is not currently
	defined.
	(get_current_source_symtab_and_line): Initialize sal.pc and
        sal.end fields.
	(set_current_source_symtab_and_line): Mark argument as const.
	* source.h: Update declarations and comments.
	* linespec.c (decode_line_1): Replace call to removed routine above.
	* stack.c (print_frame_info_base): Ditto.
	* cli/cli-cmds.c (edit_command): Ditto.
	(list_command): Ditto.