Support for .NET PDBs

[michal-kapala]

Out of curiosity I tried using pdb_symbols example to parse a custom-made C# dll, sadly nothing but module addresses could be parsed.

For my example the following symbol kinds appeared as not implemented:

• 0x404 (OEM)
• 0x1120 (MANSLOT)
• 0x1129 (TOKENREF)
• 0x112a (GMANPROC)

Implementing the above symbols would be a fair step for supporting .NET binaries (at least those built with standard Visual Studio Build Tools).
I'd gladly contribute these though I'm not familiar with the inner PDB format, I assume it's just taken off Microsoft/microsoft-pdb. If there's any other source of guidance on the used format I would appreciate that a lot.

[mitsuhiko]

Some limited support is in symbolic. If there is appetite it could be moved into the PDB crate but the formats and the use is rather different. https://docs.rs/symbolic/12.4.1/symbolic/debuginfo/ppdb/index.html

[michal-kapala]

I submitted #146 with .NET-specific symbol reading, S_OEM is missing proper buffer reading but other than that i think the changes are ready. The changes are testable with pdb_symbols.rs example (i only included managed procedures and slots aka methods and their local variables), i'd appreciate a review/merge.

I tested on PDBs targeting .NET Framework 4.8, attempts to parse .NET 6 symbols resulted in error dumping PDB: UnrecognizedFileFormat. Below you can see an example output with the source code of a corresponding C# method.