bpo-19896: Add typecodes 'q' and 'Q' to multiprocessing.sharedctypes (#2741)

* bpo-19896: Add typcodes 'q' and 'Q' to multiprocessing.sharedctypes. Patch by Antony Lee.

* Add NEWS entry.

* Slightly tweak NEWS entry

Make it clear this is more of a fix rather than a new feature.