More uses of ui_out_emit_tuple

More uses of ui_out_emit_tuple

This patch adds a few more uses of ui_out_emit_tuple.  In these cases
a slightly more complicated change was needed.  This also adds
annotate_arg_emitter, for use in stack.c, to avoid having to introduce
a new scope and reindent the code for a single call.

ChangeLog
2017-04-22  Tom Tromey  <tom@tromey.com>

	* stack.c (print_frame_arg): Use ui_out_emit_tuple,
	annotate_arg_emitter.
	* breakpoint.c (print_mention_watchpoint)
	(print_mention_masked_watchpoint): Use ui_out_emit_tuple.
	* annotate.h (struct annotate_arg_emitter): New.