Add and require primary key binding signatures on signing keys

Also, fix keyFlags of signing subkeys.

Also, store Issuer Key ID and Embedded Signature in unhashed rather
than hashed subpackets.

test/security/unsigned_subpackets.js

@@ -78,7 +78,7 @@ async function makeKeyValid() {
   // add key capability
   fake.keyFlags[0] |= enums.keyFlags.encrypt_communication;
   // create modified subpacket data
-  pusersig.unhashedSubpackets = fake.write_all_sub_packets();
+  pusersig.read_sub_packets(fake.write_hashed_sub_packets(), false);
   // reconstruct the modified key
   const newlist = new List();
   newlist.concat([pubkey, puser, pusersig]);