[Dovecot] [patch] make <chroot>/./<home> a config option.

Hi, I think that the wu-ftp style chroot /./ should be a configurable option.

In our servers we have some home directories in /chroot-web/./username (where web users can upload their web sites in a chrooted environment) and all imap mail in /mail-disk/username.

We are planning a dovecot migration from our modified version of uw-imap and we noticed that the chroot in /chroot-web/ can't be disabled.

This patch adds the bool option home_slash_dot_slash_chroot (feel free to change this name to something easier to understand). Setting this to "no" disables the wu-ftp style /./ chroot.

I hope this feature can be considered useful and soon included in dovecot.

Regards, Diego Liziero.