don't arrange layers on disabled monitors

call setfullscreen() in setmon()

this will help when sending to another monitor a fullscreen client
and also will prevent a crash when a client request fullscreen when it has no monitor

prevent segfault when destroying monitors

also don't count unmapped surfaces for exclusive zone
and exclusive_focus is now of type `void *`

Revert "Revert "various improvements to layer surface""

This reverts commit c017916d35795cf85e5181907f5e97a1d702612a.

Revert "various improvements to layer surface"

see https://github.com/djpohly/dwl/issues/289#issuecomment-1231287114

This reverts commit 226051974060746d02d787ac1ef70b6267ee51b4.

various improvements to layer surface

- remove various useless assignments of layersurface->mon
- styles changes
- do not set wlr_layer_surface->output to NULL at destroy

conform the idle inhibitor protocol

previously we disable idle tracking simply due to the fact that it exist

new function to notify keyboard enter

prevent an infinite loop if try to use focusmon() with all monitors disabled

don't try to set monitor for clients in createmon()

this is done in updatemons()

set monitor for clients that don't have one in updatemons()

only if selmon is enabled and the clients are mapped

set monitor for clients that don't have one on monitor creation

don't respect size hints for fullscreen clients

Fixes: #292

change type of c->bw: int -> unsigned int

reorder isfullscreen in Client definition

initialize to zero the box used in commitnotify()

fix crash when setting a custom mode

rework outputmgrapplyortest()

first disable requested monitors, then enable and/or change mode, x and y, etc.
This is mostly what sway does

check client_from_wlr_surface() returning NULL in urgent()

fix #281

fix segfault if parent->mon is unset