Add VS2012 support.

Note we will use the same project files but different Platform toolset based on the VS version.
By default we will use the "v110_xp" platform which supports XP as its name shows.

git-svn-id: https://peerblock.googlecode.com/svn/trunk@641 d3e0e2f6-51e0-11de-b413-c5e99dc0a8e2
build_VS2010.bat: Simplify the MSBuild command.

MSBuild is in PATH since we call "%VS100COMNTOOLS%vsvars32.bat".

git-svn-id: https://peerblock.googlecode.com/svn/trunk@642 d3e0e2f6-51e0-11de-b413-c5e99dc0a8e2