I'm reverting one of the changes made to exception.cpp in r151717. I'm unsure...

I'm reverting one of the changes made to exception.cpp in r151717.  I'm unsure what the change was trying to do, but it didn't do the right thing for __APPLE__.  So instead of trying to guess what was intended, I'm just putting it back the way it was.

llvm-svn: 151727