Support VC11 (Visual Studio 2012)

Add check to detect VC11 and set appropriate output name
Add _VARIADIC_MAX for googletest compilation

Change-Id: Ie3bac435946d240454a6506e4612c6fc8d1781ed
Reviewed-on: http://review.couchbase.org/28029
Reviewed-by: Mark Nunberg <mnunberg@haskalah.org>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>