gdb: Split func_command into two parts.

gdb: Split func_command into two parts.

The func_command function is used to emulate the dbx 'func' command.
However, finding a stack frame based on function name might be a useful
feature, and so the core of func_command is now split out into a
separate function.

gdb/ChangeLog:

	* stack.c (select_and_print_frame): Delete.
	(struct function_bounds): Move struct within function.
	(func_command): Most content moved into new function
	find_frame_for_function, use new function, print result, add
	function comment.
	(find_frame_for_function): New function, now returns a result.