i386: Fix missing break; in case statement leading to incorrectly returned FFI_BAD_AB...

i386: Fix missing break; in case statement leading to incorrectly returned FFI_BAD_ABI (#437)

* i386: Add missing break triggering dead store static analyzer checks.

Register calling sequence is being reported as bad ABI instead of working as intended.

Found-by: Clang Static Analysis
Signed-off-by: Jeremy Huddleston Sequoia <jeremyhu@macports.org>
* Mark ffi arm sysv entry points as private_extern.

Signed-off-by: Jeremy Huddleston Sequoia <jeremyhu@macports.org>
* x86_64: Add implementation of compact unwind for ffi_call_unix64.

Signed-off-by: Jeremy Huddleston Sequoia <jeremyhu@apple.com>