Add CAP-78 - Host function for performing limited TTL extensions

[dmkozh]

No description provided.

[anupsdf]

We also have one more host function to extending current contract (extend_current_contract_instance_and_code_ttl). Should we provide this min/max extension to that one as well?

[dmkozh]

Should we provide this min/max extension to that one as well?

I don't think so, the new function can just be used with the current contract address as well. extend_current_contract_instance_and_code_ttl is the first function we have introduced, as at the time we haven't realized that it might be useful to extend other contracts as well (in the contract factory scenario).