Parse the TPI (type information) stream of PDB files.

Parse the TPI (type information) stream of PDB files.

This parses the TPI stream (stream 2) from the PDB file. This stream
contains some header information followed by a series of codeview records.
There is some additional complexity here in that alongside this stream of
codeview records is a serialized hash table in order to efficiently query
the types. We parse the necessary bookkeeping information to allow us to
reconstruct the hash table, but we do not actually construct it yet as
there are still a few things that need to be understood first.

Differential Revision: http://reviews.llvm.org/D19840
Reviewed By: ruiu, rnk

llvm-svn: 268343