identifier namespace by renaming non standard functions and variables
such that they have a leading underscore. The library will use those
names internally. Weak aliases are used to provide the original names
to the API.
This is only the first part of this change. It is most of the functions
which are implemented in C for all NetBSD ports. Subsequent changes are
to add the same support to the remaining C files, to assembly files, and
to the automagically generated assembly source used for system calls.
When all of the above is done, ports with weak alias support should add
a definition for __weak_alias to <sys/cdefs.h>.
domainname isn't RFC1035 compliant. Also ensure that the length <=
YPMAXDOMAIN (which is less than what RFC1035 allows).
* use _yp_invalid_domain in the public front-ends, instead of using
hand-rolled checks
* fix a typo
