* Use RETSIGTYPE for signal handler return values.

* Got rid of static buffers; we now use cucul_free() to free exported
    buffers.
  * Fixed light background in the ANSI exporter by adding escape sequences for
    most terminal emulators.

are unable to cleanly restore the state.

a network port, we could have guessed.

+ Changed port to 51914 (rationale: it's 0xCACA; so okay, it's outside
      the registered ports area, but we'd never be accepted anyway).
    + Retry network sends in caca_get_event(), too.
    + Have a per-client buffer in case of network congestion. If that buffer
      gets full, just drop it and start again at the next frame.
    + Set the window title to "caca for the network".
    + Do not send the ANSI buffer's terminating \0.
    + Restore the SIGPIPE handler on close.
    + Set window size to 80x24 instead of 80x25.

writes. Currently works very badly with more than one client.

network_display() so that new clients immediately get the contents
    of the canvas and do not need to wait for a caca_display() call.

they can force a resize. We need to find a way to make those specific
    cucul - caca interactions unavailable to the clueless user.