re PR libfortran/19032 (modulo generates wrong result for divisor 1 and -1)

fortran/
PR fortran/19032
* trans-intrinsic.c (gfc_conv_intrinsic_mod): Update comment
in front of function to match the standard.  Correct handling
of MODULO.

testsuite/
PR fortran/19032
* gfortran.dg/intrinsic_modulo_1.f90: New.
* gfortran.fortran-torture/execute/intrinsic_mod_ulo.f90: Add
tests with divisor -1.

From-SVN: r92645