Wait for packets to be accepted before returning from writev

Without this, the caller has no way to know when it's safe to reuse the
buffer. This also works around this problem:

http://lists.xenproject.org/archives/html/xen-users/2014-07/msg00067.html
Merge pull request #11 from talex5/wait-until-accepted

Wait for packets to be accepted before returning from writev
Bump to 1.1.2
Revert "Wait for packets to be accepted before returning from writev"

Linux dom0 and Xen have been patched to fix the underlying bug, and
this work-around made things really slow.

This reverts commit aa5061b8ffdc2e34968e80ed745ffd77372fa358.