Adds translation support for the register restores used in rseq mangling.
Adds a test of a fault/signal in native rseq code by taking advantage of the lack of xmm support to have different behavior in the instrumented vs native executions.
I hit this while trying to force a restart for i#4019 in a custom test, but it could happen in regular execution with an asynchronous signal.
Issue: #2350 (closed)