server: fix conditions for fds in wl_socket_destroy

0 is also a valid fd, and needs to be closed.

On error we set fd to -1. We need to also initialize fds to -1, so we do
not accidentally close stdout on error.

While fixing this, also remove one use-before-NULL-check.

Based on the patch by Marek.

Cc: Marek Chalupa <mchqwerty@gmail.com>
Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-by: Jasper St. Pierre <jstpierre@mecheye.net>
scanner: Use an enum to determine the type of thing we're writing out

Reviewed-by: Marek Chalupa <mchqwerty@gmail.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
scanner: Make emit_structs more explicit

"is_interface" is a really terrible name for the client or server
variants, and instead of checking whether we were passed the requests or
the events, just pass an argument through.

Reviewed-by: Marek Chalupa <mchqwerty@gmail.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
tests: make event-loop-test more explicit

Check value set in handler against an explicit value instead of:
  assert(value);

also add one assert() for non-NULL value.

Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
event-loop: make signalfd non-blocking

When we add more that one source to a signal, then wayland will
block in wl_event_loop_dispatch. This is due to the attampt to read
from signal's fd each time the source is dispatched.

  wl_event_loop_add_signal(loop, SIGINT, ...);
  wl_event_loop_add_signal(loop, SIGINT, ...);

  /* raise signal .. */

  /* we got two fd's ready, both for the one SIGINT */
  epoll_wait(...) = 2

  [ for (i == 0) ]
      source1->dispatch() --> read(fd1);
  [ for (i == 1) ]
      source2->dispatch() --> read(fd2); /* blocking! */

Reading from fd2 will block, because we got only one signal,
and it was read from fd1.

Signed-off-by: Marek Chalupa <mchqwerty@gmail.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
tests: add one more test for event-loop signal source

Test if when we get a signal, all signal sources for that signal
get dispatched.

Signed-off-by: Marek Chalupa <mchqwerty@gmail.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
util: list corruption is bad
server: Don't expose wl_display as a global

The idea here was that once upon a time, clients could rebind wl_display
to a higher version, so we offered the ability to rebind it
here. However, this is particularly broken. The existing bind
implementation actually still hardcodes version numbers, and it leaks
previous resources, overwriting the existing one.

The newly bound resource *also* won't have any listeners attached by the
client, meaning that the error and delete_id events won't get delivered
correctly. Unless the client poked into libwayland internals, it also
can't possibly set up these handlers correctly either, so the client
will sustain errors and leak all deleted globals.

Since this never worked correctly in the first place, we can feel safe
removing it.
server: Add a new, simpler API for creating and binding globals
server: Deprecate the old wl_global_create API