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 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.

Note that the MPI_SIZEOF bindings were already fixed in the release branch in  514ea9f6cc59bcd6426ec3f524ffdfb4279491e0.
Please add a comment explaining C vs. Fortran compiler subtlety here (and why new code won't link against the dummy lib).