Readd MD4.

Sadly this is needed by wpa_supplicant for NTLM hashes.

Change-Id: I1c362c676a11ee01f301ff6fbd33d0669396ea23
Reviewed-on: https://boringssl-review.googlesource.com/1620
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/include/openssl/digest.h b/include/openssl/digest.h
index 76d6677..291a548 100644
--- a/include/openssl/digest.h
+++ b/include/openssl/digest.h
@@ -76,6 +76,7 @@
  * The following functions return |EVP_MD| objects that implement the named hash
  * function. */
 
+OPENSSL_EXPORT const EVP_MD *EVP_md4(void);
 OPENSSL_EXPORT const EVP_MD *EVP_md5(void);
 OPENSSL_EXPORT const EVP_MD *EVP_sha1(void);
 OPENSSL_EXPORT const EVP_MD *EVP_sha224(void);