IMAP: setting flags, and body fetching works now.

* The direct methods in BMailProtocol now forward the request to the
looper; it's no longer the mail_daemon's responsibility to know
anything about that protocol.
* It's in desperate need of refactoring, but it doesn't hurt to add
it to the repository as is.

IMAP,POP3,NewMailNotification: fixed x86_64 build.

* Notifier::HeaderFetched(): fixed the method signature (go figure how it could
build on x86).
* POP3: fSizes type is now std::vector<size_t> instead of BList. Please review.
off_t might be a better choice.
* added the mail_daemon add-ons to the Haiku package again.

IMAP: let mail retrieval scale better.

* We now also maintain a mail index -> UID array in IMAPMailbox.
* Instead of fetching the message entries by a fixed range of UIDs, we use the
message count, and get the entries by index.
* Likewise, in FetchHeadersCommand, we now get a list of UIDs rather than a
range. This makes it possible to only download exactly the headers we want.
* Extended FetchCommand to be able to dynamically build a sequence list from
a list of UIDs.
* Besides the suboptimal body fetching (one at a time, due to holes in the
IMAP specification), we should now be able to retrieve the messages with
pretty much optimal performance, while retaining an acceptable responsiveness
to user requests.

IMAP: work in progress of downloading the mail body.

* Most things are in place now, we just try to download the body to the
wrong file, as the final location is currently unknown.
* Added local only kPartialMessage flag for mails, but it's not being
used yet.

imap: Work in progress of connection setup.

* SelectCommand now correctly encodes the mailbox name again.
* Hierarchy separators from the LIST/LSUB commands are now properly parsed,
and taken into account.
* Folders in the file system are now created for mailboxes on the server,
supporting hierarchical mailbox names.
* A connection worker now has an IMAPFolder that handles the local side of the
mailbox, and an IMAPMailbox that handles the server side.
* Connection workers are now created/deleted, and setup correctly. They will
now also wait in case they don't have a mailbox until they get some.

IMAP,POP3,NewMailNotification: fixed x86_64 build.

* Notifier::HeaderFetched(): fixed the method signature (go figure how it could
build on x86).
* POP3: fSizes type is now std::vector<size_t> instead of BList. Please review.
off_t might be a better choice.
* added the mail_daemon add-ons to the Haiku package again.

IMAP: let mail retrieval scale better.

* We now also maintain a mail index -> UID array in IMAPMailbox.
* Instead of fetching the message entries by a fixed range of UIDs, we use the
message count, and get the entries by index.
* Likewise, in FetchHeadersCommand, we now get a list of UIDs rather than a
range. This makes it possible to only download exactly the headers we want.
* Extended FetchCommand to be able to dynamically build a sequence list from
a list of UIDs.
* Besides the suboptimal body fetching (one at a time, due to holes in the
IMAP specification), we should now be able to retrieve the messages with
pretty much optimal performance, while retaining an acceptable responsiveness
to user requests.

IMAP: work in progress of downloading the mail body.

* Most things are in place now, we just try to download the body to the
wrong file, as the final location is currently unknown.
* Added local only kPartialMessage flag for mails, but it's not being
used yet.

imap: Work in progress of connection setup.

* SelectCommand now correctly encodes the mailbox name again.
* Hierarchy separators from the LIST/LSUB commands are now properly parsed,
and taken into account.
* Folders in the file system are now created for mailboxes on the server,
supporting hierarchical mailbox names.
* A connection worker now has an IMAPFolder that handles the local side of the
mailbox, and an IMAPMailbox that handles the server side.
* Connection workers are now created/deleted, and setup correctly. They will
now also wait in case they don't have a mailbox until they get some.