Cherry pick of https://bitbucket.org/lindenlab/mesh-development/changeset/9cea44ebea3b by don, to fix old viewer crashes in mesh regions

indra/llprimitive/llprimitive.h

@@ -103,6 +103,7 @@ public:
 		PARAMS_LIGHT    = 0x20,
 		PARAMS_SCULPT   = 0x30,
 		PARAMS_LIGHT_IMAGE = 0x40,
+		PARAMS_MESH     = 0x50,
 	};
 	
 public:

indra/newview/llviewerobject.cpp

@@ -4877,6 +4877,10 @@ void LLViewerObject::adjustAudioGain(const F32 gain)
 
 bool LLViewerObject::unpackParameterEntry(U16 param_type, LLDataPacker *dp)
 {
+	if (LLNetworkData::PARAMS_MESH == param_type)
+	{
+		param_type = LLNetworkData::PARAMS_SCULPT;
+	}
 	ExtraParameter* param = getExtraParameterEntryCreate(param_type);
 	if (param)
 	{