msgpack as fvwm <-> modules <-> bindings communicator

[ThomasAdam]

FVWM was written before any formal message parsing libraries existed. Currently, the communication protocol that FVWM uses is a packed structure which is shoved down a pipe, which the receiving end has registered interest in by locking on to various messages which are sent.

Other libraries exist to abstract away this message construction, such as msgpack which allows for other binary data to be considered (rather than packing unsigned longs down a pipe, which is how FVWM does this currently).

Another benefit is that other languages have native msgpack bindings, which would allow for agnostic FVWM APIs to be created to allow scripting in any language. This is similar to how neovim does things, for example.

Hence, it would be interesting to:

• Replace the current FVWM <-> Module messages with msgpack;
• Expose interfaces for modules to listen on certain events;

[ThomasAdam]

This has now mostly been completed via FvwmMFL -- will eventually move in to the core.