Add more primops for atomic ops on byte arrays

Summary:
Add more primops for atomic ops on byte arrays

Adds the following primops:

 * atomicReadIntArray#
 * atomicWriteIntArray#
 * fetchSubIntArray#
 * fetchOrIntArray#
 * fetchXorIntArray#
 * fetchAndIntArray#

Makes these pre-existing out-of-line primops inline:

 * fetchAddIntArray#
 * casIntArray#

Test Plan: Ran new unit test. Looked at generated assembly code.

Reviewers: simonmar

Subscribers: hvr, fryguybob, simonmar

Differential Revision: https://phabricator.haskell.org/D15