[flang] Add atomic_cas to the list of intrinsics

[flang] Add atomic_cas to the list of intrinsics

Add the atomic subroutine, atomic_cas, to the list of intrinsic
subroutines and check one of its arguments for a coindexed object.
Create a new function, CheckAtomicKind, that will be used for the
atomic subroutines that have arguments that can be either of type
int and of kind atomic_int_kind or of type logical and of kind
atomic_logical_kind.

Reviewed By: jeanPerier

Differential Revision: https://reviews.llvm.org/D135835