* authenc.c (net_write): Rewrite in terms of netwrite()

	* authenc.c (net_write): Rewrite in terms of netwrite()

	* configure.in: Check for vsnprintf().

	* ext.h: New prototypes for netprintf, netprintf_urg,
	netprintf_noflush, netwrite, netputs.

	* slc.c: Fix to use new NETOBUF-handling functions.

	* state.c: Fix to use new NETOBUF-handling functions.

	* telnetd.c: Fix to use new NETOBUF-handling functions.

	* termstat.c: Fix to use new NETOBUF-handling functions.

	* utility.c: General rework to be more paranoid about
	bounds-checking of NETOBUF and NFRONTP.  Abstract away
	interactions with NETOBUF to eliminate explicit references to
	NFRONTP in many places.
	(netwrite): New function; copies a buffer to the
	NETOBUF "ring buffer", checking bounds and calling netflush() if
	needed.
	(netputs): New function; calls netwrite() with a nul-terminated
	string.
	(netprintf, netprintf_ext): New function; wrap sprintf() with
	bounds checking for use with NETOBUF.
	(netprintf_urg): New function; like netprintf() except sets neturg
	to point at last char written.
	(netprintf_noflush): New function; like netprintf() except
	silently fails if NETOBUF is full.
	(ttloop, printoption, printsub, printdata): Fix to use new
	NETOBUF-handling functions.

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@13669 dc483132-0cff-0310-8789-dd5450dbe970