Hyper-V support.

Adds Hyper-V KVP daemon. This is a user space program to
communicate key-value-pairs to the hypervisor, through the
hyper-v kernel drivers.

Primary usage is to get the IP of the vm from the hypervisor. Boot2docker is already building and including the hyper-v kernel modules which get loaded automatically if running within hyper-v. The daemon is benign if the modules are not loaded. The daemon is 43K.