Modified c files (simulator/src/c/NengoGPU/*.c) to be compatible with VS C++ 2010 compiler. Moved variable declaration to the beginning of each function because VS C++ is strict about that.

Added VS C++ 2010 project and solution file. Solution file is able to build to both 32-bit and 64-bit versions of the JVM.

Modified NEFGPUInterface.java to display more detailed error messages.