Provide information about "openssl dgst" -hmac option.

apps/dgst.c

@@ -229,6 +229,7 @@ int MAIN(int argc, char **argv)
 		BIO_printf(bio_err,"-keyform arg    key file format (PEM or ENGINE)\n");
 		BIO_printf(bio_err,"-signature file signature to verify\n");
 		BIO_printf(bio_err,"-binary         output in binary form\n");
+		BIO_printf(bio_err,"-hmac key       create hashed MAC with key\n");
 #ifndef OPENSSL_NO_ENGINE
 		BIO_printf(bio_err,"-engine e       use engine e, possibly a hardware device.\n");
 #endif

doc/apps/dgst.pod

@@ -18,6 +18,7 @@ B<openssl> B<dgst>
 [B<-verify filename>]
 [B<-prverify filename>]
 [B<-signature filename>]
+[B<-hmac key>]
 [B<file...>]
 
 [B<md5|md4|md2|sha1|sha|mdc2|ripemd160>]
@@ -78,6 +79,10 @@ verify the signature using the  the private key in "filename".
 
 the actual signature to verify.
 
+=item B<-hmac key>
+
+create a hashed MAC using "key".
+
 =item B<-rand file(s)>
 
 a file or files containing random data used to seed the random number