Putting the privateSnippetExecutor() assembly code as inline asm
inside an otherwise empty C++ function helps, for some reason.

Use the actual _Unwnd_Exception and __cxa_exception definitions as
used by Apple (from opensource.apple.com libunwind and libcppabi
sources) instead of guessing.

Change-Id: I1ef22a9c0c664d3a357b9a6474406141f53cc490