Improve __load__.bro creation for .bif.bro stubs.

The new loader scripts should not try to @load .bif.bro scripts that
were part of a build of an earlier Bro version, but have since had their
.bif file removed.
change the sumstats table that tracks recent intermediate requests
back to create interval.

In this instance a read expiry actually makes much less sense.
Merge remote-tracking branch 'origin/topic/jsiwek/bif-loader-scripts'

BIT-1175 #merged

* origin/topic/jsiwek/bif-loader-scripts:
  Improve __load__.bro creation for .bif.bro stubs.
Updating submodule(s).

 [nomail]
Merge remote-tracking branch 'origin/fastpath'

* origin/fastpath:
  change the sumstats table that tracks recent intermediate requests back to create interval.