For a function that seems to be provided using different calls under different
versions of UNIX (e.g., memcpy vs. bcopy), I made up a different name and
used that.  The portlib code implementing the function then maps onto whichever
call is appropriate for the host system.

For a function that has the same name on all systems on which it is present,
but is simply missing on some systems (e.g., strcasecmp), I use that name
and provide code to implement it.