--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.

#ifndef __FTS_LUCENE_PLUGIN_H
#define __FTS_LUCENE_PLUGIN_H

#include "fts-api-private.h"

extern struct fts_backend fts_backend_lucene;

void fts_lucene_plugin_init(void);
void fts_lucene_plugin_deinit(void);

#endif