PR fortran/21875 Internal Unit Array I/O, NIST
* fortran/trans-io.c (gfc_build_io_library_fndecls): Add field for
array descriptor to IOPARM structure.
* fortran/trans-io.c (set_internal_unit): New function to generate code
to store the character (array) and the character length for an internal
unit.
* fortran/trans-io (build_dt): Use the new function set_internal_unit.