(Fx_hide_tip): Avoid unnecessary work when there's

(Fx_hide_tip): Avoid unnecessary work when there's
nothing to do.  Bind inhibit-quit.
(tip_frame): Make it a Lisp_Object.
(x_create_tip_frame): Set tip_frame after it has been added to
Vframe_list.
(Fx_show_tip): Don't set tip_frame here.
(image_cache_refcount, dpyinfo_refcount) [GLYPH_DEBUG]: New
variables.
(unwind_create_frame, unwind_create_tip_frame): New functions.
(Fx_create_frame, x_create_tip_frame): Handle errors signaled
while a frame is only partially constructed.