Reset: hook to clear the effects cache.

simgear/scene/material/Effect.hxx

@@ -176,6 +176,8 @@ Effect* makeEffect(SGPropertyNode* prop,
 bool makeParametersFromStateSet(SGPropertyNode* paramRoot,
                                 const osg::StateSet* ss);
 
+void clearEffectCache();
+
 namespace effect
 {
 /**

simgear/scene/material/makeEffect.cxx

@@ -270,4 +270,10 @@ Effect* makeEffect(SGPropertyNode* prop,
     return effect.release();
 }
 
+void clearEffectCache()
+{
+    OpenThreads::ScopedLock<OpenThreads::ReentrantMutex> lock(effectMutex);
+    effectMap.clear();
+}
+
 }