Make sure memset() is defined by including string.h
Notified by Oscar Jacobsson <oscar@jacobsson.org>

crypto/des/read2pwd.c

diff --git a/crypto/des/read2pwd.c b/crypto/des/read2pwd.c
index f0eef23..b4720c3 100644
--- a/crypto/des/read2pwd.c
+++ b/crypto/des/read2pwd.c
@@ -109,6 +109,7 @@
  * [including the GNU Public Licence.]
  */
 
+#include <string.h>
 #include <openssl/des.h>
 #include <openssl/ui.h>