Import an updated version of avsm's ec2.sh AMI bundling script

Signed-off-by: Mike McClurg <mike.mcclurg@citrix.com>
Merge pull request #13 from mcclurmc/ec2-script

Import an updated version of avsm's ec2.sh AMI bundling script
mirari run --unix now runs unikernels for the UNIX backend.
Add fd-send-recv as a dependency for unikernels if target is unix-direct
Better error message on Ctrl+C
Put an IP on tapX, in order for tuntaposx to work.
bump to 0.9.3
Do not use OPAM compiler switches any more, as that's done in the packaging now