increase wl_compositor version

Now scene will handle sending the preferred buffer scale

References: https://gitlab.freedesktop.org/wlroots/wlroots/-/merge_requests/4269

Merge branch 'main' into wlroots-next

do not use wl_event_loop for signal handling

ΔSLOC: -4

Fixes: https://github.com/djpohly/dwl/issues/456
Fixes: https://github.com/djpohly/dwl/issues/459

Remove now-unneeded call to motionnotify

This appears to have been here for the side effect of updating the drag
icon's position.

Remove unused icon variable

Make drag_icon a persistent scene node

If there is no current drag icon, this node will be empty, but we now
have `drag_icon != NULL` as an invariant.  This allows us to eliminate a
conditional, since there's no harm in moving an empty node's coordinates
around with the pointer.

ΔSLOC: -1

properly destroy scene

ΔSLOC: +1

chase wlroots!4220

References: https://gitlab.freedesktop.org/wlroots/wlroots/-/merge_requests/4220

Line saver: LISTEN_STATIC macro

This parallels the LISTEN macro for statically allocated listeners, and
it allows us to remove almost all of the global wl_listener
declarations.

This also fixes a bug with the axisnotify listener, which was declared
with a compound literal.  At block scope, these have automatic storage
duration [1], so the listener was no longer valid after setup()
returned.  (The option to declare it static explicitly was standardized
in C23, if that ever gains suckless traction.)

ΔSLOC: -27

[1]: https://en.cppreference.com/w/c/language/compound_literal#Explanation

Unify signal handling under wl_event_loop

Merge our signal handlers into a single function and let Wayland deal
with all the struct sigaction stuff.

ΔSLOC: -3

Line saver: follow "local = wlr->data = obj" pattern

There were still a couple of places where we could use this handy
multiple assignment to save a line.

ΔSLOC = -3

Merge remote-tracking branch 'upstream/main' into wlroots-next

Separate drag icon from layers array and Lyr enum

If we treat the drag icon as distinct from other layers (it doesn't have
contents that are interactive, focusable, etc.), then we can iterate
over layers meaningfully with a simple for loop.

ΔSLOC: -8

schedule a frame after commmiting gamma

not doing it, may freeze the output or do not actually change the gamma until
creating a client

use detached output states to set gamma

Revert "use wlr_scene_output_build_state() to set gamma"

This reverts commit 65f68e76437275a0c1c25279af646f726e213b6d.

Don't bother with ignoring SIGCHLD

It added complexity, especially with the differences in behavior between
handled and ignored signals across an exec().

Reset ignored signal handler in spawn() as well

fix startup_cmd SIGCHLD handler

Ignored handlers are not reset by exec() calls

drop KDE idle support

use ext-idle-notify-v1 instead