Create director_common.swg for language-indep code

Move -DSWIG_DIRECTOR_STATIC handling there, so this is now supported for
all languages with director support, not just Python and PHP.

Source/Modules/python.cxx

@@ -967,6 +967,7 @@ public:
 
     if (directorsEnabled()) {
       // Insert director runtime into the f_runtime file (make it occur before %header section)
+      Swig_insert_file("director_common.swg", f_runtime);
       Swig_insert_file("director.swg", f_runtime);
     }