Correct ECIES shared key length check
Correct ECIES shared key length check

* Ensure the ECIES shared key is padded with zero bytes if it's
  smaller than the requested key length.
* Split the ECIES shared key error into two;
  one for when the generated key is too big for the params
  and one for when it's nil (point of infinity returned by the
  curve scalar multiplication).

maran/go-ethereum,maran/go-ethereum,maran/go-ethereum,pki-io/ecies,maran/go-ethereum,maran/go-ethereum,maran/go-ethereum,maran/go-ethereum,maran/go-ethereum,obscuren/ecies,maran/go-ethereum