[llvm-pdbdump] Abstract some of the YAML/Raw printing code.

[llvm-pdbdump] Abstract some of the YAML/Raw printing code.

There is a lot of duplicate code for printing line info between
YAML and the raw output printer.  This introduces a base class
that can be shared between the two, and makes some minor
cleanups in the process.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@301728 91177308-0d34-0410-b5e6-96231b3b80d8