use $self special variable instead of self in %extend

git-svn-id: https://swig.svn.sourceforge.net/svnroot/swig/trunk/SWIG@9533 626c5289-ae23-0410-ae9c-e8d60b6d4f22

Examples/test-suite/director_extend.i

@@ -5,7 +5,7 @@
 {
    virtual int dummy()          // Had to remove virtual to work
    {
-      return self->getFooBar();
+      return $self->getFooBar();
    }
 };