veyron2: veyron2.Init function for new API.
veyron2: veyron2.Init function for new API.

The veyron2.Init function will do the following.
(1) Construct an empty context.
(2) Calls a profileInitFunc that returns a RuntimeX instace and an initialized context.
(3) Returns the *context.T and a context.CancelFunc.

Change-Id: I4130499bba7955c57291654ca1aa7504bdb78a2d

vanadium/go.v23,vanadium/go.v23,vanadium/go.v23