Add an HKDF (RFC 5869) implementation
diff --git a/scripts/generate_errors.pl b/scripts/generate_errors.pl
index ac0fbff..7290b87 100755
--- a/scripts/generate_errors.pl
+++ b/scripts/generate_errors.pl
@@ -31,7 +31,7 @@
 
 my @low_level_modules = qw( AES ARC4 ASN1 BASE64 BIGNUM BLOWFISH
                             CAMELLIA CCM CMAC CTR_DRBG DES
-                            ENTROPY GCM HMAC_DRBG MD2 MD4 MD5
+                            ENTROPY GCM HKDF HMAC_DRBG MD2 MD4 MD5
                             NET OID PADLOCK PBKDF2 RIPEMD160
                             SHA1 SHA256 SHA512 THREADING XTEA );
 my @high_level_modules = qw( CIPHER DHM ECP MD