X11: set menu entries to same length

While testing the new mouse action menus, it was quite annoying
to try and hit some shorter entries. Make all the selectable entries
the same maximum length, and with text left justified.

doc/fixes3-7-0.txt

@@ -1371,6 +1371,7 @@ X11: with 'slow' resource set to False, the pop up yn_function didn't always
 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
+X11: set all selectable menu lines to the same length, left justified
 
 
 General New Features