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.

interface/wx/propgrid/property.h

@@ -516,7 +516,7 @@ wxPG_PROP_CLASS_SPECIFIC_3          = 0x00400000
 
     Note that when displaying the value, sign is omitted if the resulting
     textual representation is effectively zero (for example, -0.0001 with
-    precision of 3 will become 0.0 instead of -0.0). This behaviour is unlike 
+    precision of 3 will become 0.0 instead of -0.0). This behaviour is unlike
     what C standard library does, but should result in better end-user
     experience in almost all cases.