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.

include/wx/osx/msgdlg.h

@@ -24,7 +24,7 @@ public:
 #if wxOSX_USE_COCOA
     ~wxMessageDialog();
 #endif
-    
+
     virtual int ShowModal();
 
 #if wxOSX_USE_COCOA