[PDB] Support pointer types in the native reader.

[PDB] Support pointer types in the native reader.

In order to start testing this, I've added a new mode to
llvm-pdbutil which is only really useful for writing tests.
It just dumps the value of raw fields in record format.
This isn't really ideal and it won't allow us to test some
important cases, but it's better than nothing for now.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@341729 91177308-0d34-0410-b5e6-96231b3b80d8