[llvm-pdbdump] Add support for dumping symbols from Yaml -> PDB.

Previously we could round-trip type records from PDB -> Yaml ->
PDB, but for symbols we could only go from PDB -> Yaml.  This
completes the round-tripping for symbols as well.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297625 91177308-0d34-0410-b5e6-96231b3b80d8
6 files changed