BUILDFIX WIN fixing windows build error

converted a struct to a class, cleaning up a forward declaration that caused windows build issues.

indra/llappearance/llavatarappearance.h

@@ -272,7 +272,7 @@ class LLAvatarAppearance : public LLCharacter
 protected:
 	virtual LLTexLayerSet*	createTexLayerSet() = 0;
 protected:
-	struct LLMaskedMorph;
+	class LLMaskedMorph;
 	typedef std::deque<LLMaskedMorph *> 	morph_list_t;
 	struct BakedTextureData
 	{