o Digital UNIX needs to check for *snprintf() before -ldb is added to LIBS

since -ldb includes a bogus snprintf().
o Add forward refs for struct mbuf and struct rtentry for Digital UNIX.
o Reorder some functions in snprintf.c to fix -Wall
o Add missing includes to fix more -Wall

auth/sudo_auth.c

@@ -50,6 +50,7 @@
 #include <sys/param.h>
 #include <sys/types.h>
 #include <pwd.h>
+#include <time.h>
 
 #include "sudo.h"
 #include "sudo_auth.h"