Implement CallbackFilterIterator, issue #1715

This implements CallbackFilterIterator. It also makes the basic tests pass. Moved the test from zend/bad to zend/good.

The 002 tests in the folder diff because of the output messages from the compiler versus PHP's. However, they appear to be giving the right failures. Wasn't sure whether the group ignores those, patches up the expect file, corrects the messages from the compiler, etc.