Use custom allocators in all plugins

[nemequ]

Many libraries used by plugins do not support specifying malloc/free functions. I'd like to file bugs (and potentially patches) against the libraries to get the functionality added, this is a long-term meta-bug to track those issues.

• [ ] brotli — C++ (currently)
• [x] bsc
• [x] csc
• [ ] doboz — C++
• [x] fari
• [x] lzg
• [ ] gipfeli — C++
• [x] pithy (still unsupported, but plugin disabled for security reasons, on track to be removed)
• [ ] snappy — C++
• [ ] yalz77 — C++, returns a new std::string
• [ ] zling — C++
• [ ] zpaq — C++, unsupported, but it looks like everything goes through a custom allocx func, shouldn't be hard to put together a patch
• [ ] zstd — Unsupported, I think