This reverts commit add38856.

If a folder's directory is missing 'tmp' sub-directory, but it has
all the other 'cur' and 'new' directories, then try to create
the 'tmp' to get all three required directories.

It's because some backup tools can drop the 'tmp' directories.

This was reported as: https://bugzilla.redhat.com/show_bug.cgi?id=995702

The change for disabled weak ciphers require at least NSS 3.14, thus
weak ciphers are enabled, if it's compiled with older NSS. In case
any server will require either weak ciphers or SSL v2 (while there
really should not anyone use it these days), then two environment
variables were added:

   CAMEL_SSL_V2_ENABLE=1 - to have SSL v2 enabled, otherwise it's disabled,
       regardless what camel providers request (they usually request v2 and
       v3 together)

   CAMEL_SSL_WEAK_CIPHERS=1 - to enable weak ciphers, almost the same as
       before; otherwise these are disabled and only those covered by
       NSS_SetDomesticPolicy() are enabled

These are added to the group of one for SSL V2 compatible hello:

   CAMEL_SSL_V2_HELLO=1 - to force SSL v2 compatible hello on SSL connections

Do not call "connect" when changing online state in 'connecting' state,
and similar for "disconnect", to prevent a deadlock, if this change is
called within "connect" or "disconnect" function itself.

Do not set CAMEL_DISCO_STORE_OFFLINE when the CamelService reports
something other than CAMEL_SERVICE_CONNECTED.  That would lock the
store into offline mode such that further connection attempts will
simply invoke connect_offline() and never actually establish a new
server connection.

(cherry picked from commit dde0172c)

(cherry picked from commit 0d07dbba)

(cherry picked from commit 7a7a9603)

A client application cancelling an operation should not terminate the
parser thread.  The parser thread completes the operation even if the
client is no longer interested in the result.  The parser thread loop
must only be broken out of on an I/O error, parsing error, the server
hanging up, or application shutdown.

(cherry picked from commit fab4ebc8)

Once again, the code expected the opposite, which led to runtime
warnings and failed connection to the server.

The code, incorrectly, assumed that the store is always connected
when a list of folders is requested, but the actual connection
happens only during command invocation, after whose successful
finish it's ensured that there is defined also a stream.

This can be reproduced by creating a new NNTP account and trying
to manage subscription. The first try fails, console is filled with
runtime warnings, the second try shows list of available folders.

Enable this feature only for backends we are completely sure it works.
Only enabled for local calendars (file backend) for now.

The 'old_component' parameter can be NULL, but the function expects it
always an a valid ECalComponent object, which made notifications about
changes missing for such cases (like detaching a recurring event instance).

It's too hard to distinguish from other provider errors when using
general error codes here, thus rather use CAMEL_SERVICE_ERROR_URL_INVALID.