add bugzilla integration hook. example of writing hook in python. hook updates bugzilla bugs when it sees commit comments that mention bug id, such as "i fixed bug 77". only bugzilla 2.16 supported yet, but easy to extend. bugzilla versions have different schema, i have not used later than 2.16.

# should print nothing
# should print ? b/x
? b/x
# should print A b/x
A b/x
# should forget b/x
forgetting b/x
# should print nothing