__gxx_personality_v0 update. This is completely untested code. But my brain...

__gxx_personality_v0 update.  This is completely untested code.  But my brain is scrambled and I wanted to get it checked in.  Code review from anyone who knows anything at all about personality functions would be much appreciated.  What is in here is borrowed heavily from llvm/examples/ExceptionDemo/ExceptionDemo.cpp.  There are some calls to abort() that should probably be changed to return an error code instead.  There may be encodings under readEncodedPointer that need to be implemented.  And my handling of type_info is almost a complete guess.

llvm-svn: 147680