X11 popup yn_function resizing

When X11_yn_function() re-uses a popup widget to issue a prompt
and get the player's response, make it resize properly.  I'm not
sure why the old hack for that apparently worked for some folks
and not for me, or why this does work for me.  At least it does.

Also, make the minimum popup width be 25 characters so that
really short prompts don't result in tiny popups.  Since the
popup appears at whatever spot the pointer happens to be sitting,
it isn't always immediately noticeable when the player is using
the keyboard rather than the pointer.

doc/fixes37.0

@@ -1,4 +1,4 @@
-NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.459 $ $NHDT-Date: 1613777904 2021/02/19 23:38:24 $
+NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.460 $ $NHDT-Date: 1613957400 2021/02/22 01:30:00 $
 
 General Fixes and Modified Features
 -----------------------------------
@@ -673,6 +673,8 @@ X11: avoid 'bad Atom X Error' when perm_invent is enabled (seemingly window
 	manager dependent)
 X11: toggling 'perm_invent' off via 'O' didn't dismiss persistent inventory
 	window
+X11: with 'slow' resource set to False, the pop up yn_function didn't always
+	resize properly when re-used
 X11: (possibly X11+OSX): if persistent inventory was displayed at time of
 	end-of-game prompting, prompting would stall until that window was
 	manually dismissed