- added X(), Y(), Z() access functions to AActor.

This commit is just preparation for upcoming changes to completely encapsulate the coordinate info in AActor because I'm going to have to work with an altered version of actor.h that cannot be committed without breaking the engine.
With this file present in the repo before work is started the changes can be committed piece by piece.

src/actor.h

@@ -1155,6 +1155,20 @@ public:
 	}
 
 	bool HasSpecialDeathStates () const;
+
+	fixed_t X() const
+	{
+		return x;
+	}
+	fixed_t Y() const
+	{
+		return y;
+	}
+	fixed_t Z() const
+	{
+		return z;
+	}
+
 };
 
 class FActorIterator