Made the Boost Build msvc toolset use correct setup scripts in case of some stripped down MSVC 8.0+ distributions like the MSVC express 9.0 version distributed with the Microsoft Platform SDK that come without the vcvarsall.bat script.
Added new Boost Build msvc configuration options: setup-amd64, setup-i386 & setup-ia64 so separate setup commands can be specified for different target platforms. These overrule any global setup setting and do not get any parameters passed to them.
Documented how the Boost Build msvc toolset locates its default setup scripts depending on the actual MSVC distribution used.
[SVN r46135]
Jurko Gospodnetić