Split out evdev headers (input.h, input-event-codes.h, uinput.h) into their
own port, devel/evdev-proto, and update those to be current with the Linux
4.19 kernel.  This is done in order to be able to update the rest of the
FreeBSD input stack, which is forthcoming.

By splititng out the evdev headers we can update them independent of other
updates in v4l_compat, which makes it easier for the graphics team to keep
track of them and keep them updated as needed.

Update devel/libevdev from 1.4.4 to 1.5.9 instead of trying to make it work
with the updated headers.  This will be further updated.

Update devel/py-evdev from 0.5.0 to 0.8.1 instead of trying to make it work
with the updated evdev headers.

Update consumers to use devel/evdev-proto rather than multimedia/v4l_compat
as needed, and bump portrevisions.

This is the first step in getting the FreeBSD input stack (libevdev,
libinput and so on) updated to newer versions.

Many thanks to all who have helped out with testing, code and exp-runs.
Apologies if I've forgotten to add any names.

PR:		222905, 217248, (based on, in part), 233787 (exp-run)
Submitted by:	Greg V, wulf
Tested by:	tcberner, kde
Exp-run by:	antoine
Approved by:	portmgr (antoine)
Obtained from:	FreeBSDDesktop development repo
		https://github.com/FreeBSDDesktop/freebsd-ports/tree/feature/input
		https://github.com/FreeBSDDesktop/freebsd-ports/tree/feature/input-ports