Don't include strings.h because of Windows.

This is a follow on to dab64ff9bef8aa3f0edc7aff01263ade81ba14fa.

Change-Id: I01644f058030c0fac3f636871cc55a082edf51f1
diff --git a/crypto/cipher/cipher.c b/crypto/cipher/cipher.c
index db1da19..4bb4196 100644
--- a/crypto/cipher/cipher.c
+++ b/crypto/cipher/cipher.c
@@ -58,7 +58,6 @@
 
 #include <assert.h>
 #include <string.h>
-#include <strings.h>
 
 #include <openssl/err.h>
 #include <openssl/mem.h>