Use rpcgen's -C option, although using it for non-headers breaks K&R
support.  A local copy of yp.h is built to avoid adding
-I/usr/include/rpcsvc to CFLAGS.  This version of yp.h differed from
<rpcsvc/yp.h> only in not declaring prototypes.

Fixed style bugs.

- Completely recoded the ypmatch cache code. The old code could leak
  memory: it would allow the cache to grow, but never
  shrink. The new code imposes the following limits:

	o The cache is capped at a limit of 5 entries.
	o Each entry expires after five seconds, at which point
	  its slot is freed.
	o If an insertion is to be done and all five slots
	  are filled, the oldest entry is forcibly expired
	  to release its slot.

  Also, the cache is implemented on a per-binding basis rather than
  having a global cache covering all bindings. This means that each
  bound domain has its own 5 slot cache.

- Changed clntudp_create() to clntudp_bufcreate() so that the
  xmit/recv message buffer sizes can be set explicitly. NIS transactions
  are rarely much larger than 1024 bytes since YPMAXRECORD is 1024.
  The defaults chosen by clntudb_create() are actually much larger
  than needed. I set the xmit buffer to a little over 1024 and the
  recv buffer to a little over 2048. This saves a few Kbytes for each
  NIS binding.

- Add my name to the copyright. I think I've made enough changes to
  this file to merit it. :)

Note: these changes should go into the 2.2.x branch, but I'm waiting
on feedback from a tester to see if the cache fixes solve the reported
memory leak problem.

so that all these makefiles can be used to build libc_r too.

Added .if ${LIB} == "c" tests to restrict man page builds to libc
to avoid needlessly building them with libc_r too.

Split libc Makefile into Makefile and Makefile.inc to allow the
libc_r Makefile to include Makefile.inc too.

This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.

Boy, I'm glad we're not using sup anymore.  This update would have been
insane otherwise.

_yp_dobind() checks to see if a fork() happens (by checking PIDs) and
invalidates all bindings if it finds itself in a newly created child
process. (This avoids sharing RPC client handles and socket descriptors
with the parent, which would be bad.) Unfortunately, it summarily
calls clnt_destroy() on the handles, which may result in the destruction
of a descriptor that isn't really a socket.

This is fixed by replacing the explicit call to clnt_destroy() with a
call to _yp_unbind(), which deals with potentially hosed socket descriptors
an a safe manner.

This is basically a one-liner. Once I confirm that it fixes Christoph's
problem, I'd like permission to put it in the 2.2-RELENG branch.