initialize members better

dtool/src/prc/configVariableFilename.I

@@ -40,10 +40,12 @@ INLINE ConfigVariableFilename::
 ConfigVariableFilename(const string &name, const Filename &default_value, 
                        const string &description, int flags) :
 #ifdef PRC_SAVE_DESCRIPTIONS
-  ConfigVariable(name, VT_filename, description, flags)
+  ConfigVariable(name, VT_filename, description, flags),
 #else
-  ConfigVariable(name, VT_filename, string(), flags)
+  ConfigVariable(name, VT_filename, string(), flags),
 #endif
+  _value_seq(-1),
+  _value_stale(true)
 {
   _core->set_default_value(default_value);
   _core->set_used();