Added a thread-safe and robust wrapper for APR pools.

See http://redmine.imprudenceviewer.org/issues/590
and https://jira.secondlife.com/browse/SNOW-596

indra/newview/lltexturecache.cpp

@@ -743,9 +743,6 @@ void LLTextureCacheWorker::endWork(S32 param, bool aborted)
 
 LLTextureCache::LLTextureCache(bool threaded)
 	: LLWorkerThread("TextureCache", threaded),
-	  mWorkersMutex(NULL),
-	  mHeaderMutex(NULL),
-	  mListMutex(NULL),
 	  mHeaderAPRFile(NULL),
 	  mReadOnly(TRUE), //do not allow to change the texture cache until setReadOnly() is called.
 	  mTexturesSizeTotal(0),