cohttp-0.11.2 upgrade
cohttp-0.11.2 upgrade

Signed-off-by: Jon Ludlam <e7e3380887a8f95cc9dc4f0d51dedc7e849a287a@citrix.com>

thomassa/vhd-tool,simonjbeaumont/vhd-tool,djs55/vhd-tool,euanh/vhd-tool,djs55/vhd-tool,euanh/vhd-tool