Rewrite of the sqimap_get_small_header_list function.

Rewrite of the sqimap_get_small_header_list function.
Now we can handle returned fetch responses with a different order of
returned arguments. UID i.e. can be properly detected if it is returned
after the HEADER data.
Another issue I fixed is adapting the msgs_id_str to 1:* in case we request all
headers for a mailbox.
If we don't do that the msgs_id_str can become pretty large and in my case
it was 12kb large and the imap server returned a BYE, querystring to long.

We should inspect the last issue better because there are situations where I
can still trigger the error. Setting the number of messages to display to a
large value would cause a BYE again.

git-svn-id: https://svn.code.sf.net/p/squirrelmail/code/trunk/squirrelmail@4872 7612ce4b-ef26-0410-bec9-ea0150e637f0