fix a minor memory leaking flaw for SH-895: some mild memory leaking (partially)

indra/llimage/llimageworker.cpp

@@ -38,6 +38,12 @@ LLImageDecodeThread::LLImageDecodeThread(bool threaded)
 	mCreationMutex = new LLMutex(getAPRPool());
 }
 
+//virtual 
+LLImageDecodeThread::~LLImageDecodeThread()
+{
+	delete mCreationMutex ;
+}
+
 // MAIN THREAD
 // virtual
 S32 LLImageDecodeThread::update(U32 max_time_ms)

indra/llimage/llimageworker.h

@@ -73,6 +73,8 @@ class LLImageDecodeThread : public LLQueuedThread
 	
 public:
 	LLImageDecodeThread(bool threaded = true);
+	virtual ~LLImageDecodeThread();
+
 	handle_t decodeImage(LLImageFormatted* image,
 						 U32 priority, S32 discard, BOOL needs_aux,
 						 Responder* responder);