re PR fortran/32979 (Implement vendor-specific ISNAN() intrinsic function)

re PR fortran/32979 (Implement vendor-specific ISNAN() intrinsic function)

        PR fortran/32979

        * intrinsic.h (gfc_check_isnan): Add prototype.
        * gfortran.h (gfc_isym_id): Add GFC_ISYM_ISNAN.
        * intrinsic.c (add_functions): Add ISNAN intrinsic.
        * check.c (gfc_check_isnan): New function.
        * trans-intrinsic.c (gfc_conv_intrinsic_isnan): New function.
        (gfc_conv_intrinsic_function): Call gfc_conv_intrinsic_isnan
        to translate ISNAN.
        * intrinsic.texi: Document ISNAN.

        * gfortran.dg/isnan_1.f90: New test.

Co-Authored-By: Tobias Burnus <burnus@gcc.gnu.org>
From-SVN: r127224