Add generalized fetch_and_add_acquire/release (for ARMv6+)

* src/atomic_ops/generalize-arithm.template
(AO_XSIZE_fetch_and_add_acquire, AO_XSIZE_fetch_and_add_release):
Add generalized template primitives based on AO_XSIZE_fetch_and_add.
* src/atomic_ops/generalize-arithm.h: Regenerate.