Fixed crash in ImapStreamParser::readParenthesizedList(): don't parse characters inside a quoted-string.

Without this fix, if the IMAP server sent the following list: "(AA ("BB)" CC))", ImapStreamParser would crash
because it would incorrectly interpret the ")" inside the quoted string "BB)" as part of the list.

Unit tests for this fix are in the Akonadi repository.

REVIEW: 100902