The big NULL replacement party part 1.

This is meant to be a safer alternative since
NULL can often be 0. Let's not rely on that.

And yes, I know this is a lot of files. This is
a safer thing to do in big commits vs for loops.

src/ScoreKeeperNormal.cpp

@@ -104,9 +104,9 @@ void ScoreKeeperNormal::Load(
 	for( unsigned i=0; i<apSteps.size(); i++ )
 	{
 		Song* pSong = apSongs[i];
-		ASSERT( pSong != NULL );
+		ASSERT( pSong != nullptr );
 		Steps* pSteps = apSteps[i];
-		ASSERT( pSteps != NULL );
+		ASSERT( pSteps != nullptr );
 		const AttackArray &aa = asModifiers[i];
 		NoteData ndTemp;
 		pSteps->GetNoteData( ndTemp );