Add support for __builtin_unwind_init.

Also, committing an #if 0'ed __builtin_setjmp and __builtin_longjmp 
implementation I've had sitting in my tree for a while.  I haven't 
enabled it because the LLVM backend support isn't complete yet.

llvm-svn: 72727
2 files changed
tree: a23a627d0246f45fde786702343b7a9e7df09575
  1. clang/
  2. llvm/