Fix keyboard navigation in Haiku

Messages for B_MOUSE_DOWN and other mouse and keyboard events now get
delivered through MessageReceived and Haiku relies on the app to forward
them back to BView to work properly. In BeOS this was not needed.

Source/stPartSquare.cpp

@@ -7,8 +7,9 @@ Distributed under the terms of the MIT Licence. */
 #include "stSong.h"
 #include "stdefs.h"
 
-stPartSquare::stPartSquare(stSong* song,Channel * chan, uint16 index ,int8 *transp,uint8 *part,uint8 *volume, BRect rect):
-	BView(rect,"partsquare", B_FOLLOW_NONE, B_WILL_DRAW )
+stPartSquare::stPartSquare(stSong* song,Channel * chan, uint16 index,
+	int8 *transp, uint8 *part, uint8 *volume, BRect rect):
+	BView(rect,"partsquare", B_FOLLOW_NONE, B_WILL_DRAW | B_NAVIGABLE)
 {
 	ch = chan;
 	s = song;
@@ -172,6 +173,7 @@ void	stPartSquare::MouseDown(BPoint)
 
 void stPartSquare::MessageReceived(BMessage *message)
 {
+	BView::MessageReceived(message);
 	Window()->DetachCurrentMessage();
 	Window()->PostMessage(message);
 }