CamelIMAPXStoreSummary has no public or private members, so no reason
to cast pointers to that type.  Stick with plain (CamelStoreSummary *).

Removed functions:

  camel_imapx_store_summary_new()

No longer used.

No longer used.

http://tools.ietf.org/html/rfc6154

Camel does not yet provide an API for applications to utilize this
information, but we can still capture it in a CamelIMAPXMailbox.

I'm still pondering a suitable application-facing API for this.  I'd
prefer to avoid stuffing this into CamelFolderInfoFlags if I can, as
Camel already overuses / abuses flag values as it is.

http://tools.ietf.org/html/rfc5465

NOTIFY replaces IDLE when available.

Convert CamelIMAPXServer to primarily use CamelIMAPXMailbox instead of
CamelIMAPXFolder, the idea being to keep all the Camel-specific policy
and limitations relegated to CamelIMAPXStore and CamelIMAPXFolder, and
just have CamelIMAPXServer be a pure IMAP client implementation.

This is a huge commit which I don't like doing, but CamelIMAPXServer,
CamelIMAPXCommand and CamelIMAPXJob are so tightly intertwined that I
was unable to split this into smaller steps.

Added functions:

  camel_imapx_command_ref_mailbox()
  camel_imapx_job_has_mailbox()
  camel_imapx_job_ref_mailbox()
  camel_imapx_job_set_mailbox()
  camel_imapx_server_create_mailbox()
  camel_imapx_server_delete_mailbox()
  camel_imapx_server_rename_mailbox()
  camel_imapx_server_subscribe_mailbox()
  camel_imapx_server_unsubscribe_mailbox()

Removed functions:

  camel_imapx_job_has_folder()
  camel_imapx_job_ref_folder()
  camel_imapx_job_set_mailbox()
  camel_imapx_server_manage_subscription()
  camel_imapx_server_create_folder()
  camel_imapx_server_delete_folder()
  camel_imapx_server_rename_folder()

Modified function signatures:

  camel_imapx_command_new()
  camel_imapx_job_matches()
  camel_imapx_server_refresh_info()
  camel_imapx_server_sync_changes()
  camel_imapx_server_expunge()
  camel_imapx_server_fetch_messages()
  camel_imapx_server_noop()
  camel_imapx_server_get_message()
  camel_imapx_server_copy_message()
  camel_imapx_server_append_message()
  camel_imapx_server_sync_message()
  camel_imapx_server_manage_subscription()
  camel_imapx_server_update_quota_info()
  camel_imapx_server_uid_search()
  imapx_parse_status()

CamelIMAPXMailbox and CamelIMAPXNamespace are closely intertwined, so
the containing data structures for them need to be introduced together.

This commit does so, and populates the data structures in memory from
untagged server responses.  It also adds CamelIMAPXServer API to access
or query the data structures.

All of this is so far unutilized.  Actually integrating these APIs into
the other parts of IMAPX will take place in subsequent commits.

New functions:

  camel_imapx_server_ref_namespaces()
  camel_imapx_server_ref_mailbox()
  camel_imapx_server_ref_selected()
  camel_imapx_server_list_mailboxes()

Removed functions:

  imapx_parse_namespace_list()

Converts a folder path to an IMAP mailbox name, which just replaces all
slashes with the mailbox separator character.  If the mailbox separator
character appears in the folder path, it is replaced with a slash.

camel_imapx_parse_mailbox() was correctly normalizing INBOX itself,
but leaving descendants of INBOX untouched.

If the IMAP server names INBOX as, let's say, "Inbox" and INBOX has
children, then we would end up parsing LIST responses like so:

    LIST "/" "Inbox"        -> "INBOX"
    LIST "/" "Inbox/Child"  -> "Inbox/Child"

This screwed up parent/child relationships in the CamelFolderInfo,
causing "INBOX" and "Inbox" to be represented as separator folders.

Converts the special INBOX mailbox to all caps, if it appears at the
beginning of 'mailbox_name'.  The 'mailbox_name' string is modified in
place.  The 'separator' character helps reliably identify descendants
of INBOX.