Fortran ABI debacle / MPI_SIZEOF

Several fixes for the Fortran bindings on the v1.8 branch:

1. Ensure a proper shared library version number is applied to the libmpi_usempi_ignore_tkr.so library (it was always 0:0:0 before this).
1. Fix MPI_SIZEOF bindings.
1. Fix the ABI debacle with regards to MPI_SIZEOF (we screwed things up with regards to gfortran >=v4.9 in v1.8.2).  See the ompi/mpi/fortran/README-v1.8-ABI.txt file for details.