Get 9p live migration support into QEMU

It’s been on the QEMU development mailing list: https://lists.nongnu.org/archive/html/qemu-devel/2014-09/msg05438.html

We need that for making 9p filesystem shares compatible with snapshots (and it’s been verified that the above patches work when applied to Debian’s qemu 2.1+dfsg-12+deb8u2 packages.

Parent Task: #5571 (closed)

Original created by @anonym on 10214 (Redmine)

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information