--with-lucene now enables lucene full text search indexing. Note that using it breaks IMAP RFC. It also seems to have problems finding texts that have special characters in them, such as email addresses. You can anyway enable it by loading fts and fts_lucene plugins and setting fts=lucene in plugin section.

/* Copyright (C) 2006 Timo Sirainen */

#include "lib.h"
#include "fts-lucene-plugin.h"

void fts_lucene_plugin_init(void)
{
	fts_backend_register(&fts_backend_lucene);
}

void fts_lucene_plugin_deinit(void)
{
	fts_backend_unregister(fts_backend_lucene.name);
}