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/Backgrounds/Makefile.am

@@ -1,6 +1,6 @@
 
 defsdatadir = $(pkgdatadir)/Backgrounds
 
-defsdata_DATA = BlueImage.jpeg 
+defsdata_DATA = BlueImage.jpeg
 
 EXTRA_DIST = $(defsdata_DATA)