evilcorpltd
Add limits to how many file transfers can be ongoing
https://toktok.ltd/spec#file-transfer-related-packets
As the file number is represented by a 1 byte number, the maximum amount of concurrent files Tox can send to a friend is 256. 256 file transfers per friend is enough that clients can use tricks like queueing files if there are more files needing to be sent.
256 outgoing files per friend means that there is a maximum of 512 concurrent file transfers, between two users, if both incoming and outgoing file transfers are counted together.
Even though Tox supports 256 files, we may want to limit it to 32 for compatibility with uTox and Toxic. qTox supports a number greater than 32.
https://github.com/TokTok/toxic/blob/a2f0f298aaa3bdefa8de632d4304400f6932e934/src/file_transfers.h#L36
https://github.com/uTox/uTox/blob/86bdb6f85d663f0ff0c6b65ac150bd57ceeaf9b1/src/file_transfers.h#L11
