[petsc-dev] Have configure reject 32bit compiles with MPI

Satish, Add to the MPI.py code that checks if it is Windows compilers and Windows MPI and 32 bit compiles and simply tells the user they need to switch to 64 bit compilers and tell them how. Barry This will lessen the silly email chases we see of people persisting with things that don't work. Plus it provides clear instructions when you are out of commission since the rest of us don't know about this issue.