support log-rotation. See the new stupid logger and the ZEO server
log-rotation signal handler for examples.

for Unix.  This allows signal handlers that don't shut down the
process to work correctly.

queries.

NullResource.

in OFS package

doing a .append().  (XXX This is necessary since
manage_setLocalRoles() accepts whatever sequence the user passes in -
which should be fixed...)

Fixed a bug in the dtml-var tag handling of the 'null' attribute. Before null would only work correctly if there was also a 'fmt' attribute. Now null correctly works with non-zero false values when there isn't a 'fmt' option.