Documented module Udp
Merge pull request #26 from vbmithr/doc

Documentation for module Udp in the direct backend
Updated doc for module Nettypes in the UNIX backend
Updated documentation of module Nettypes in the direct backend
Fixed a syntax error in doc
Merge pull request #27 from vbmithr/doc

Doc for modules Nettypes
Normalized the doc of module Ethif for the direct backend