devel/libevdev, devel/libmtdev: advertise evdev-proto as API dependency

[jbeich]

Summary

libevdev/libmtdev cannot be used unless evdev-proto is installed. requiring evdev-proto upstream projects that use libevdev/libmtdev no longer need to check for FreeBSD-specific package.

$ fgrep -r linux/input.h /usr/local/include
/usr/local/include/libevdev-1.0/libevdev/libevdev.h:#include <linux/input.h>
/usr/local/include/libevdev-1.0/libevdev/libevdev.h: * linux/input.h shipped with libevdev.
/usr/local/include/libevdev-1.0/libevdev/libevdev.h: * @include linux/input.h
/usr/local/include/libevdev-1.0/libevdev/libevdev.h: * meaning, matching the axis names in linux/input.h. Some devices merely
/usr/local/include/mtdev.h:#include <linux/input.h>

[jbeich]

Drop evdev-proto from libinput consumers as well

[• hselasky]

I don't see any issues here. And I'm not a ports expert :-)

[wulf]

linux/input.h is a list of magic numbers required at build time only. It should be kept in BUILD_DEPENDS IMO.