Fix to support vmmouse auto-detection in x11-servers/xorg-server

[Thomas Hellstrom]

Hi!

Attached is a modified patch to the FreeBSD x11-servers/xorg servers 
port to support vmmouse auto-detection which has been broken at least 
since 10.3 I've used the 11.1 ports tree as a base.

I'm not sure this is the right way to submit improvements. Please let me 
know otherwise.

BTW is there a chance to get the devd backend into xorg git?

Thanks,

Thomas Hellström, VMware