Restore previous structure ABI behavior for bit-fields with the packed attribute...

Restore previous structure ABI behavior for bit-fields with the packed attribute for PS4 targets.

An ABI change was introduced in r254596 that modified structure layouts when the 'packed' attribute was used on one-byte bitfields. Since the PS4 target needs to maintain backwards compatibility for all structure layouts, this change reintroduces the old behavior for PS4 targets only. It also introduces PS4 specific cases to the relevant test.

Patch by Matthew Voss.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@310388 91177308-0d34-0410-b5e6-96231b3b80d8