Fix CPU plugin on Win7 x64

This pull request contains 2 changes:
* Migrate solution file to Visual Studio 2012 (not the express version)
* Fix Github issue #8 and make the CPU plugin work under Win7 x64 (not tested on Win32, but it should work)
If you do not like the solution file migration, please cherry pick the fix only.
Thanks for the hint. Fixed by pull request #55