Use the correct macro: OMPI_HAVE_FORTRAN_REAL16

Using the "#if defined(ompi_fortran_real16_t)" band-aid that I applied
in r29165 wasn't correct because if the compiler doesn't have a
fortran REAL16 type, then OMPI may well #define ompi_fortran_real16_t
to be empty, which then expands to Badness in the macro.  Hence, use
OMPI_HAVE_FORTRAN_REAL16, which will also be 0 or 1.
Fix typo/misspelling in variable name.