*stack.c: Include valprint.h.

	*stack.c: Include valprint.h.
	(disassemble_next_line): New enum.
	(show_disassemble_next_line): New function.  Show the current
	value of disassemble-next-line.
	(gdb_disassembly_stub_args): New struct for argument passing
	between function do_gdb_disassembly and function
	gdb_disassembly_stub.
	(gdb_disassembly_stub): New function.  Helper for
	gdb_disassembly.
	(do_gdb_disassembly): New function.  Use TRY_CATCH to catch
	the exception from the gdb_disassembly because it will be
	broken by filter sometime.
	(print_frame_info): If disassemble-next-line is set to auto
	or on and doesn't have the line debug messages for $pc,
	output the next instruction.
	If disassemble-next-line is set to on and there is line debug
	messages, output assembly codes for next line.
	(_initialize_stack): Make the "set disassemble-next-line"
	command an auto-boolean command.  Change its class to
	class_stack.  Place it in the top level set list.  Extend help
	to describe the auto mode.