racket/gui: adjust label size on some controls

Extra margins added by instantiating `message%' inside
`radio-box%', etc., made labels line up especially badly.

pkgs/gui-pkgs/gui-lib/mred/private/wx/cocoa/radio-box.rkt

@@ -83,6 +83,7 @@
                                            RacketImageButtonCell)
                             numberOfRows: #:type _NSInteger (if horiz? 1 (length labels))
                             numberOfColumns: #:type _NSInteger (if horiz? (length labels) 1)))])
+                (tellv cocoa setIntercellSpacing: #:type _NSSize (make-NSSize 2 2))
                 (for ([label (in-list labels)]
                       [i (in-naturals)])
                   (let ([button (tell cocoa 

pkgs/gui-pkgs/gui-lib/mred/private/wxlitem.rkt

@@ -42,6 +42,7 @@
   (define (make-label label proxy p font)
     (and label 
          (let ([l (make-object wx-message% #f proxy p label -1 -1 null font)])
+           (send l x-margin 0) (send l y-margin 0)
 	   (send l skip-enter-leave-events #t)
            (send l skip-subwindow-events? #t)
            l)))