[Dovecot] v2.2.12 released

http://dovecot.org/releases/2.2/dovecot-2.2.12.tar.gz http://dovecot.org/releases/2.2/dovecot-2.2.12.tar.gz.sig

POP3 server code changes rarely, so I haven't spent time adding automated testing for it. So of course now that it changed in v2.1.11 there was a bug that caused it to crash most of the time (except for the test case I was using while developing it). This release fixes it, no other changes.