Bug 1049136 - Stop using the TouchEventInterceptor interface in LayerView as it introduces an unnecessary layer of abstraction. r=wesj

This makes it clearer what the implications of returning true from
PanZoomController.onTouchEvent are. Rather than having arbitrary
TouchEventInterceptor implementations stop receiving events, this makes
it clear that the only thing that stops is the events getting delivered
to Gecko.
Bug 1049136 - Add a method to convert MultiTouchInputs to WidgetTouchEvents. r=mwu

Original code by Mason Chang posted on bug 970751; modified by Kartikaya Gupta
for use in bug 1049136.
Bug 1049136 - Hook up touch event handling for apz-fennec. r=wesj,snorp
Bug 1049136 - Add native-code awareness of the Java UI thread so we can do thread assertions. r=snorp
Bug 1050797 - Remove some dead code. r=rnewman