Instantiate MESSAGEMAN first. (#1399)

This fixes a well-formed warning, but does it break anything?

It's not clear off hand. Having this up for discussion.

(Matt McCutchen <matt@mattmccutchen.net>: Cherry picked from commit
a565a27da8c5278846c06585cb6e218ff8f0f1b7 with a conflict resolution.
This commit fixes a crash on startup in MessageManager::Broadcast when I
build StepMania with -DCMAKE_BUILD_TYPE=Release and g++ 6.3.1 on Fedora
25.  Apparently g++ is optimizing out the "this != NULL" on the grounds
that calling a method on a null pointer has undefined behavior, so the
"m_Logging" is a null dereference.)

src/MessageManager.cpp

@@ -207,8 +207,7 @@ void MessageManager::Unsubscribe( IMessageSubscriber* pSubscriber, MessageID m )
 
 void MessageManager::Broadcast( Message &msg ) const
 {
-	// GAMESTATE is created before MESSAGEMAN, and has several BroadcastOnChangePtr members, so they all broadcast when they're initialized.
-	if(this != NULL && m_Logging)
+	if(m_Logging)
 	{
 		LOG->Trace("MESSAGEMAN:Broadcast: %s", msg.GetName().c_str());
 	}

src/StepMania.cpp

@@ -1041,8 +1041,10 @@ int sm_main(int argc, char* argv[])
 	// This needs PREFSMAN.
 	Dialog::Init();
 
-	// Create game objects
+	// Set up the messaging system early to have well defined code.
+	MESSAGEMAN	= new MessageManager;
 
+	// Create game objects
 	GAMESTATE	= new GameState;
 
 	// This requires PREFSMAN, for PREFSMAN->m_bShowLoadingWindow.
@@ -1162,7 +1164,6 @@ int sm_main(int argc, char* argv[])
 	SONGMAN->UpdatePopular();
 	SONGMAN->UpdatePreferredSort();
 	NSMAN 		= new NetworkSyncManager( pLoadingWindow );
-	MESSAGEMAN	= new MessageManager;
 	STATSMAN	= new StatsManager;
 
 	// Initialize which courses are ranking courses here.