Merge pull request #3 from thomassa/io_nice_cp7327

CP-7327 nice and ionice config options for sparse_dd.conf
Upgrade to cohttp-0.11.2

Signed-off-by: Jon Ludlam <jonathan.ludlam@citrix.com>
Merge pull request #10 from jonludlam/great_stringext_rename

Great stringext rename
Merge branch 'master' into forupstream/merge-to-master

Conflicts:
	src/cohttp_unbuffered_io.ml
	vhd-tool.obuild
Merge pull request #14 from djs55/forupstream/merge-to-master

Use the latest vhd-tool