support for visual studio 2008 and 64 bit

Currently the only option to build a 64 bit project is to run qt either:

• create a 32bit project and manually add a 64bit build from within visual studio
• open a 64 bit visual studio command prompt (after changing the qt path to a 64bit version of qt) and build the project using "vcbuild"

All this could be resolved by allowing a 32 bit and 64 bit Qt Version to coexist in the same QTDIR and creating a Visual Studio Solution with both 32 and 64 bit buildcommands.