Move CodeViewTypeStream to DebugInfo/CodeView

Ability to parse codeview type streams is also needed by
DebugInfoPDB for parsing PDBs, so moving this into a library
gives us this option.  Since DebugInfoPDB had already hand
rolled some code to do this, that code is now convereted over
to using this common abstraction.

Differential Revision: http://reviews.llvm.org/D19887
Reviewed By: dblaikie, amccarth

llvm-svn: 268454