[CR] Make INTEGER(BIGNUM *other_value) API public in Titan API

Summary

There's a need from TitanSim to make INTEGER(BIGNUM *other_value) API public in Titan API.

Steps and/or TTCN-3 code to reproduce

What is the current bug behavior?

The API call is not public

What is the expected correct behavior?

The API call can be called

Relevant logs and/or screenshots

Possible fixes

Titan version

8.0.0

Platform details (OS type and version)

Any

/cc @aknappqwt