Add support for vsock
This adds the ability to use virtual sockets (AF_VSOCK address family) in waypipe. It is useful when running waypipe in virtual machines, especially in headless mode.
The easiest way to test it is to create a QEMU virtual machine with a vsock device, e.g.:
-device vhost-vsock-pci,guest-cid=3
Run waypipe on host:
waypipe --vsock -s 1234 client
Launch an application from guest:
waypipe --vsock -s 1234 server weston-terminal
Fixes #72 (closed)