Create an emulation/43bsd directory and move the recently modified

Create an emulation/43bsd directory and move the recently modified
compatibility syscalls there. Any future work on the COMPAT_43 code
should be split from the rest of the kernel and moved here.

Everything in the kernel that explicity uses the osockaddr structure
has been modified to include "emulation/43bsd/43bsd_socket.h".

There was one case where struct osockaddr was used in userland,
talk/talkd.  This commit has a temporary fix for talk/talkd.