Fix error handling

[abooij]

Our error handling is rather underdeveloped. In particular, we have several instances where we simply call error which should really be some kind of "abort and return -1" statement (for the C ABI).

For socket handling (reading and writing, as in Graphics.Sudbury.Socket.Wayland), we need to deal with sockets that close. (oh and when looking at this, please also compare the size limits for reads and writes with libwayland)

[abooij]

The major omissions in CABI.Client are an analogue of libwayland's display_fatal_error (fired on e.g. read/write errors) and display_protocol_error (fired when we have received a wl_display.error message).