Log Message:
devel/hs-atomic-primops: import hs-atomic-primops-0.8.4

After GHC 7.4 a new casMutVar# primop became available, but it's difficult
to use safely, because pointer equality is a highly unstable property in
Haskell. This library provides a safer method based on the concept of
Tickets.

Also, this library uses the "foreign primop" capability of GHC to add
access to other variants that may be of interest, specifically, compare and
swap inside an array.

Note that as of GHC 7.8, the relevant primops have been included in GHC
itself. This library is engineered to work pre- and post-GHC-7.8, while
exposing the same interface.