RDP compositor take 4

This patch is the fourth version of the FreeRDP based compositor.
Changes from last version:
 * dropped tiling for raw surfaces (not required)
 * corrected remoteFx encoding to have all rects of a damage
   event into a single remoteFx frame
 * added a mode to read the client socket in an env variable
 * handle NS codec
Merge pull request #2 from hardening/rdp-compositor-4

RDP compositor take 4