This update adds support for dovecot 2.4, allows to limit the amount
of threads via the maxthreads option and fixes several bugs.
For 2.3, e. g. optionally use:
plugin {

fts = xapian
fts_xapian = lowmemory=500 maxthreads=4 partial=3 verbose=0
fts_autoindex = yes
fts_enforced = yes
<...>

}