Baseline Unix 98 (Single Unix Specification) sockets interface

This interface was generated semi-mechanically from the Unix 98 
documentation available here:

  http://www.opengroup.org/onlinepubs/007908799/xnsix.html

Because struct and constant definitions vary in their details from platform 
to platform while the function interface doesn't (in general), the more
stable function interfaces have been split into hopefully platform-common
files, with struct and constant data in platform-specific files.
