#31 crawler does not recover after segfault

[Mikhail Bessonov]

The new filter subsystem does not survive the second
fork(). Crawler used to fork a new harvester when the
old one died for some reason (e.g., weird HTML in the
downloaded page). Now the last screams in the log are:

Selected [bow_filter] filtering method as defaut
bow_words_read_from_fp: The vocabulary map has already
been created.
22:07:21 OASIS_CRAWLER Parent got signal SIGABRT