QPID-4575 Visual Studio 2012 - Add VS2012 to cmake shell script.
Tested with CMake 2.8.6.
* This patch trivially adds VS2012 to the version pulldown and passes the right args to CMake.
* CMake now gets a Boost_COMPILER value to allow older (2.8.6) versions of CMake to find boost. This is probably not necessary with newer CMake.

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1444937 13f79535-47bb-0310-9956-ffa450edef68