Remove trailing whitespace.

Also, the script is a one-liner, stolen from [1]:

ack --print0 -l '[ \t]+$' | xargs -0 -n1 perl -pi -e 's/[ \t]+$//'

[1]
https://stackoverflow.com/questions/149057/how-to-remove-trailing-whitespace-of-all-files-recursively

WindowMaker/plmenu.ja.in

@@ -91,11 +91,11 @@
     ("Wine Shades",   EXEC, "wdwrite WindowMaker WorkspaceBack '(vgradient, \"#600040\", \"#180010\")'")
     ),
    ("イメージ", OPEN_MENU, "-noext #wmdatadir#/Backgrounds $HOME/GNUstep/Library/WindowMaker/Backgrounds WITH wmsetbg -u -t")
-   ),   
+   ),
   ("設定をテーマとしてセーブ", SHEXEC, "getstyle -t $HOME/GNUstep/Library/WindowMaker/Themes/\"%a(Theme name)\""),
   ("現在のアイコンセットをセーブ", SHEXEC, "geticonset $HOME/GNUstep/Library/WindowMaker/IconSets/\"%a(IconSet name)\""),
   ("設定ユーティリティ", EXEC, "#wprefs#")
-  ), 
+  ),
  ("終了",
   ("再起動", RESTART),
   ("BlackBox をスタート", RESTART, blackbox),