Most warnings are implicit conversions, inspecting the warnings led to finding a bug in the endian-shim where htobe32 was incorrectly defined as htons instead of htonl

As we have moved forward towards automated builds using the videolan registry,
we need to focus all of our efforts into the meson build system. At this point,
the meson scripts work for building the lib and the tools for linux, windows and osx.

Also fix all warnings on macos and turn on -werror on macos builds. Fixed/workedaround errors and warnings on mingw windows build. Some still remaining. These need to be fixed before we can turn on -werror.

Unify public API where possible. Most receiver/sender functions have the same backend implementation and can be unified into universal functions. To access the specific sender/receiver structs we change to a rist_ctx struct. This can also allow us in the future to unify sender and receiver behavior without breaking the API again.