Add the new argument required by BlockController interface

The problem:

Calls to classes implementing BlockController interface in cool.module does not provide the now required $delta argument.
This is raising fatal errors with PHP7 (so setting priority to major)

Proposed solution:

Add the required argument when calling BlockController methods.

The attached patch tries to implement the proposed solution, however I'm not sure I had done it right for some cases (eg in cool_block_info())