dh: Add missing include for fprintf()

src/dh.c:824:5: warning: incompatible implicit declaration of built-in
function 'fprintf' [enabled by default]
     fprintf(stderr, "%s\n", fingerprint);
     ^

Signed-off-by: Andreas Schneider <asn@cryptomilk.org>
Reviewed-by: Jakub Jelen <jjelen@redhat.com>

src/dh.c

@@ -25,6 +25,8 @@
 
 #include "config.h"
 
+#include <stdio.h>
+
 #include "libssh/priv.h"
 #include "libssh/crypto.h"
 #include "libssh/buffer.h"