add freeze action to eosio.info and check to eosio.system.setcode

[MrToph]

Changelog

• Add freezecode action to eosio.info contract
• Implement eosio.system's setcode action to throw when setting code on a frozen account.

For the setcode action on the system contract to be executed from within nodeos (and not just the native setcode handler) we need to enable the FORWARD_SETCODE protocol feature (hash 2652f5f96006294109b3dd0bbde63693f55324af452b799ee137a81a905eed25) on the chain