Cocoa: Disable touch events.

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>