Log Message:
Update to Dovecot 1.2.11.

mbox users really should upgrade, because by sending a message with a huge
header you could basically cause a DoS (this problem exists only with v1.2.x,
not with v1.0 or v1.1).

- mbox: Message header reading was unnecessarily slow. Fetching a huge header
  could have resulted in Dovecot eating a lot of CPU.  Also searching messages
  was much slower than necessary.
- mbox, dbox, cydir: Mail root directory was created with 0770 permissions,
  instead of 0700.
- maildir: Reading uidlist could have ended up in an infinite loop.
- IMAP IDLE: v1.2.7+ caused extra load by checking changes every 0.5 seconds
  after a change had occurred in mailbox