[CodeView] Move CodeView YAML code to ObjectYAML.

This is the beginning of an effort to move the codeview yaml
reader / writer into ObjectYAML so that it can be shared.
Currently the only consumer / producer of CodeView YAML is
llvm-pdbdump, but CodeView can exist outside of PDB files, and
indeed is put into object files and passed to the linker to
produce PDB files.  Furthermore, there are subtle differences
in the types of records that show up in object file CodeView
vs PDB file CodeView, but they are otherwise 99% the same.

By having this code in ObjectYAML, we can have llvm-pdbdump
reuse this code, while teaching obj2yaml and yaml2obj to use
this syntax for dealing with object files that can contain
CodeView.

This patch only adds support for CodeView type information
to ObjectYAML.  Subsequent patches will add support for
CodeView symbol information.

llvm-svn: 304248