Fix keyword name for co_reduce.
gcc/fortran/ChangeLog:
* intrinsic.c (add_subroutines): Change keyword "operator"
to the correct one, "operation".
* check.c (gfc_check_co_reduce): Change OPERATOR to
OPERATION in error messages.
* intrinsic.texi: Change OPERATOR to OPERATION in
documentation.
gcc/testsuite/ChangeLog:
* gfortran.dg/co_reduce_2.f90: New test.
* gfortran.dg/coarray_collectives_14.f90: Change OPERATOR
to OPERATION.
* gfortran.dg/coarray_collectives_16.f90: Likewise.
* gfortran.dg/coarray_collectives_9.f90: Likewise.
Co-authored by: Steve Kargl <steve@gcc.gnu.org>