MSVC 2008 Builds: Speed Up Release Builds

MSVC 2008 Builds: Speed Up Release Builds

Use the /MP compiler option, where the build time for release builds can
be cut down by quite a bit.  This will however cause a brief warning with
debug builds due to the use of /Gm, but the code will otherwise build
normally.  Unlike the Visual Studio 2010+ builds, we can't use /d2Zi+ as
Visual Studio 2008 does not support that, so we can't get a better
debugging experience for release builds here.