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

src/wconfig.h.in

@@ -111,7 +111,7 @@
 /*
  * Some of the following options can be configured in the preference files,
  * but if for some reason they can't, these are their defaults.
- * 
+ *
  * There are also some options that can only be configured here, at compile time.
  */