Make sure vsnprintf() exists before using it. Add fallbacks.

libraries/liblutil/setproctitle.c

@@ -54,8 +54,15 @@ va_dcl
 	va_start(ap);
 #endif
 
+#ifdef HAVE_VSNPRINTF
 	buf[sizeof(buf) - 1] = '\0';
 	vsnprintf( buf, sizeof(buf)-1, fmt, ap );
+#elif HAVE_VPRINTF
+	vsprintf( buf, fmt, ap ); /* hope it's not too long */
+#else
+	/* use doprnt() */
+	chokeme = "choke me!  I don't have a doprnt() manual handy";
+#endif
 
 	va_end(ap);