Cocoa: Disable touch events.

Enabling touch events has a negative impact on overall
performance. In particular, enabling touch events seems
to disable scroll event compression, resulting scroll
processing lag.

Until we find a solution where we can have both proper
scrolling and touch events we choose scrolling over
touch events. Applications that disagree can enable 
touch events manually:

NSView *qtView = (NSView *)QGuiApplication::platformNativeInterface()->
	nativeResourceForWindow("nsview", qtWindow);
[qtView setAcceptsTouchEvents:YES];

Change-Id: I85cdd6e8c8ed8685c6cd5418c89fed6af02887cd
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@digia.com>

src/plugins/platforms/cocoa/qcocoawindow.mm

@@ -703,11 +703,6 @@ void QCocoaWindow::setNSWindow(NSWindow *window)
                                           name:nil // Get all notifications
                                           object:m_nsWindow];
 
-    // ### Accept touch events by default.
-    // Beware that enabling touch events has a negative impact on the overall performance.
-    // We probably need a QWindowSystemInterface API to enable/disable touch events.
-    [m_contentView setAcceptsTouchEvents:YES];
-
     [window setContentView:m_contentView];
 }