Boost 1.52 uses a completely different api for atomics. Not going to be supporting them. Also, fix llcalcparser in more old-boost compatible manner, and fix linux usage of apr_signal_description_get.

indra/newview/llmeshrepository.cpp

@@ -2334,7 +2334,7 @@ void LLMeshRepository::notifyLoadedMeshes()
 	//call completed callbacks on finished decompositions
 	mDecompThread->notifyCompleted();
 
-	if (!mThread->mSignal->tryLock())
+	if (!mThread->mSignal->try_lock())
 	{ //curl thread is churning, wait for it to go idle
 		return;
 	}