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/datetime.h

@@ -325,7 +325,7 @@ public:
        Copy constructor.
     */
     wxDateTime(const wxDateTime& date);
-    
+
     /**
         Same as Set().
     */
@@ -387,7 +387,7 @@ public:
        @a wxDateTime::Tm structure.
     */
     wxDateTime& Set(const Tm& tm);
-    
+
     /**
         Sets the date from the so-called Julian Day Number.