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

WPrefs.app/xpm/Makefile.am

@@ -72,5 +72,5 @@ dist_xpmdata_DATA = \
 	windowfocus.xpm \
 	workspace.xpm \
 	workspacename.xpm \
-	xis.xpm 
+	xis.xpm
 endif