Another attempt to fix Pmw loading in plugin runtime

direct/src/p3d/thirdparty.pdef

@@ -37,7 +37,8 @@ class tk(package):
     module('direct.showbase.TkGlobal',
            'direct.tkpanels',
            'direct.tkwidgets',
-           'Pmw', 'Pmw.Pmw_1_2', 'Pmw.Pmw_1_3')
+           'Pmw', 'Pmw.Pmw_1_2.lib.PmwLoader',
+                  'Pmw.Pmw_1_3.lib.PmwLoader')
 
 class sqlite(package):
     config(display_name = "SQLite Interface")