Unit tests and fixes for fork handling

The big fix is an parenthesis bug in the INIT() macro.

Also, add an initializations counter for testing fork handlers
Better INIT() macro: exploit INHERIT_ZERO and simplify

The major change here is to make a new NEED_REINIT macro that INIT() can use.
Use pthread_atfork where appropriate
Disable debugging trace outputs; they have not helped in a while