Remove all trailing spaces

No real changes, just clean up sources by removing trailing spaces from
all the non-generated files.

This should hopefully avoid future commits mixing significant changes
with insignificant whitespace ones.

samples/render/render.bkl

@@ -22,5 +22,5 @@
         <wx-lib>core</wx-lib>
         <wx-lib>base</wx-lib>
     </wx-gui-plugin>
-    
+
 </makefile>