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

WINGs/Makefile.am

@@ -18,7 +18,7 @@ libWUtil_la_LIBADD = @LIBBSD@
 EXTRA_DIST = BUGS make-rgb Examples Extras Tests
 
 
-# wbutton.c 
+# wbutton.c
 libWINGs_la_SOURCES = 	\
 	configuration.c \
 	dragcommon.c \