fix drag and drop not working

this fixes another issue where the cursor doesn't change when selecting text
but there is still an issue about not changing border color of clients during
dnd operations

Bug: https://github.com/djpohly/dwl/issues/318

avoid usage of goto

Based on this suggestion: bc72af6e2430cfb8db2f5fa1b9800c86f445b6d6#commitcomment-85592855">https://github.com/guyuming76/dwl/commit/bc72af6e2430cfb8db2f5fa1b9800c86f445b6d6#commitcomment-85592855

properly handle cursor motion when button is held

Based on: https://gitlab.freedesktop.org/wlroots/wlroots/-/merge_requests/3653

avoid setting duplicate cursor image

Reference: https://gitlab.freedesktop.org/wlroots/wlroots/-/issues/3436
Based on: https://gitlab.freedesktop.org/wlroots/wlroots/-/merge_requests/3595

destroy renderer and allocator in cleanup()

fix bad condition

fix various segfaults when selmon is NULL

change cursor surface in internal calls of motionnotify()

and call motionnotify() after unmapping a client
and when focusing a client

Fixes: https://github.com/djpohly/dwl/issues/308

remove unused variables

make more permissive exclusive focus

now you can call focusstack() while a layer surface is focused and when it gets
unmapped the newly focused clients will be actually focused

now really fix clients not being focused after unmapping a layer surface

fix clients not being focused after destroy a layer surface

Revert "remove useless check of `m` in arrangelayers()"

This partially reverts commit d14ee99661e420c8e3d8fcc6791429a0e08bd915.

Checking if the output is enabled is necessary to avoid a segfault later

remove useless check of `m` in arrangelayers()

it is supossed to avoid a crash when we pass m=NULL as argument
however it would crash anyway and also because we should not pass m=NULL

fix use of loop initial declaration

forbidden by the suckless style

fix unmanaged clients not being unlinked from the commit listener

fix segfault when unlocking swaylock on two monitor setup

wlr_*_surface_from_wlr_surface() can return NULL if the surface
is being destroyed

Fixes: https://github.com/djpohly/dwl/issues/305

don't try to move outputs when its x,y hasn't change

when using wlr_output_layout_move() wlroots internally
change the state of the output to manually configured and
when updating the layout these outputs aren't ignored by
wlroots, leaving us at our own

prior run the startup command start the backend

this allow use clients like wlr-randr in the startup command

make sure the parent is mapped prior set monitor and tags