Swap the contents of UnwindRegistersRestore and Save.

No functionality change
Upstream did this in clang r193840; doing this here too makes
upstreaming easier.

Change-Id: I9aec0435d96c09a8f55cbde703cb2744d477ed55
Merge pull request #35 from awong-dev/swap

Swap the contents of UnwindRegistersRestore and Save.