This adds the bitcoinconsensus library as a target.
This library exports 3 symbols:
- bitcoinconsensus_verify_script
- bitcoinconsensus_verify_script_with_amount
- bitcoinconsensus_version
A few manipulations are required to get the same output than autotools.
These can be later removed but are kept for now in order to not break
the software relying on the current autotools format.
Depends on D4197.