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/llplugin/llpluginprocesschild.cpp

@@ -47,7 +47,7 @@ LLPluginProcessChild::LLPluginProcessChild()
 {
 	mState = STATE_UNINITIALIZED;
 	mInstance = NULL;
-	mSocket = LLSocket::create(gAPRPoolp, LLSocket::STREAM_TCP);
+	mSocket = LLSocket::create(LLSocket::STREAM_TCP);
 	mSleepTime = PLUGIN_IDLE_SECONDS;	// default: send idle messages at 100Hz
 	mCPUElapsed = 0.0f;
 	mBlockingRequest = false;