Pad SDL: use index in pads mapping (#1154)

In onEvent(), e.controller is based on index instead of sp.id, and sp.id is not guarantee to be the same as index (when index=0, sp.id=1). As we use pads.get, the key value should be index instead of sp.id in initPad(). The previous implementation can cause problem when more than 1 Pad is connected to the system: the 2nd one can cause the 1st one disconnect.

hxd/Pad.hx

@@ -509,7 +509,7 @@ class Pad {
 		if( @:privateAccess sp.ptr == null )
 			return;
 		var p = new hxd.Pad();
-		p.index = sp.id;
+		p.index = index;
 		p.d = sp;
 		pads.set( p.index, p );
 		for( axis in 0...6 )