x11-drivers/xf86-input-wacom: new device and hotplug support

• Add device IDs for the following tablets: Intuos Draw small Intuos Art/Photo/Comic small Intuos Draw medium Intuos Art medium
• Add and enable devd(8) hotplug support
• Work around devd failing to remove stale device files opened by Xserver
• Drop Xserver 1.7 tip from pkg-message after r374982

PR: 206086
Submitted by: rozhuk.im@gmail.com