[Dovecot] howto disable indexing on dovecot-lda ?

[Adrian Minta]

Hello,

I tested with "mail_location = whatever-you-have-now:INDEX=MEMORY" and it seems to help, but in the mean time I found another option completely undocumented that seems to do exactly what I wanted:
protocol lda {
	mailbox_list_index_disable= yes

}

Does anyone knows exactly what  "mailbox_list_index_disable" does and if 
is still available in 2.0 and 2.1 branch ?