[Patch, Fortran] Add library support for coarray's atomic intrinsics

[Dominique Dhumieres]

This probably caused

/opt/gcc/work/libgomp/testsuite/libgomp.fortran/pr34020.f90:16.24:

        call atomic_add(lhs, rhs)
                        1
Error: ATOM argument at (1) to intrinsic function atomic_add shall be an 
integer of ATOMIC_INT_KIND

Dominique