bugzilla: extract optional hours from commit message and update bug time
If an 'hours' group is present in the bug matching regular expression,
and that group contains a float value, update the bug working time in
Bugzilla with those hours.
The patch adds a key 'hours' to the bug state dictionary, and adds
support for the key to the XMLRPC and XMLRPC/email access methods.
The MySQL access method is not supported; a warning is given.