tidy up some extern declarations

Update old-style definitions to ANSI, remove a couple of register
definitions along the way. Fixed gcc 4.1 build (thank you vax)

branches: 1.12.56;
Modify the licences of code written by Theo De Raadt from a 4-clause
to a 2-clause licence (retaining UCB clauses (1) and (2)), per PR
22409 from Joel Baker, approved by Theo de Raadt, and ratified by
myself - the only discrepancy being the handling of the original
clause 3 in src/usr.sbin/yppoll/yppoll.c.

add explicit casts to avoid parameter conversion warnings.

Delint.
Remove trailing ; from uses of __weak_alias(). The macro inserts this if
needed.

xdrproc_t casts

delint

If port provides __weak_alias(), provide an Standard C and POSIX pure
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>.

Fix RCSID's
printf -> warnx
Fix gcc warnings
Put locally declared functions in local.h

* implement _yp_invalid_domain, which returns non-zero if the given
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

branches: 1.4.2;
Pull down yp/xdr fixes from release branch.

branches: 1.3.2;
these files all need to include <string.h>

Use a constant struct timeval for yp timeouts instead of creating
a new struct timeval in each yp function at runtime.
Check arguments and return YPERR_BADARGS if invalid.

Split yp_all, yp_master, and yp_other out of yplib.c; makes some static
executables a bit smaller.