Clean up the arm64 setjmp.

Note that this doesn't address the fact that we don't save/restore the
real-time signals. But it does let us pass the tests we currently fail.

Bug: 16918359
Change-Id: I063a6926164289a71026a412da7f5dd2ca9a74b3
Merge "Clean up the arm64 setjmp."
Clean up arm setjmp family.

Bug: 16918359
Change-Id: I9b986bdbdbaefe9d9896a820ee8cfe860adfe5c5
Merge "Clean up arm setjmp family."