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.

src/common/uiactioncmn.cpp

@@ -89,7 +89,7 @@ bool wxUIActionSimulatorImpl::MouseDragDrop(long x1, long y1, long x2, long y2,
     MouseDown(button);
     MouseMove(x2, y2);
     MouseUp(button);
-    
+
     return true;
 }