Implement managed procedures and local var slots

[michal-kapala]

Overview

I added support for the managed symbols missing from .NET PDBs:

• S_TOKENREF
• S_OEM (basic)
• S_LMANPROC
• S_GMANPROC
• S_MANSLOT
• S_MANSLOT_ST

I also added support for:

• S_ENVBLOCK
• S_SECTION
• S_COFFGROUP

Now it's possible to view the names of properties, constructors, methods and local variables of C#-originating PDBs (could be helpful for Visual Basic, I haven't checked). I extended pdb_symbols example to include the managed symbols.