new dovecot 2.4 support in current beta has broken imap_capability causing clients to fail AUTH

There is a bug in debian6_dovecot2.4.conf.master

imap_capability=+SPECIAL-USE XLIST

This overrides imap_capability instead of extending it causing for example thunderbird desktop clients to fail during login, before AUTH. Because of missing IMAP4rev1, which is required to detect IMAP support.

This bug results in: CAPABILITY +SPECIAL-USE XLIST AUTH=PLAIN AUTH=LOGIN

instead of: CAPABILITY IMAP4rev1 LOGIN-REFERRALS ID ENABLE IDLE SASL-IR LITERAL+ AUTH=PLAIN AUTH=LOGIN

Removing the config line for imap_capability fixed it for me, but did not send +SPECIAL-USE XLIST then. I don't know if it is still required for anything.