Add support for other typeinfo encodings in the ExceptionDemo.

The old jit always uses DW_EH_PE_absptr, but MCJIT can use other encodings.
This is in preparation for adding EH support to MCJIT, but not directly
related, so I am committing it first.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180883 91177308-0d34-0410-b5e6-96231b3b80d8