WinRT: Proper error handling in socket engine's "bind"

runOnXamlThread should always return S_OK (causes exceptions otherwise)
so we need another way of error reporting to the outside (hr reference).
A failed hr is reported to the outside (of the lambda) and interpreted
as an unknown error.

Specific error cases like the given address not being a local address
or the given address being in use already are handled inside the lambda.
The specificErrorSet variable is necessary in these cases so that the
error is not overwritten by unknownError.

Change-Id: I198d66fe97726d5127bf31e50c7eff3363d5259c
Reviewed-by: Maurice Kalinowski <maurice.kalinowski@qt.io>