Merging the imap_consistency branch.

Merging the imap_consistency branch.

The main aim of this branch was to make the IMAP
code function in the same manner as the ODBC code
does, eliminating the need for so many IMAP-specific
code chunks. The focal point of all of this work was
to make the various macros (e.g. RETRIEVE, DISPOSE)
functionally equivalent.

While doing the above work, I also fixed a few bugs
that I came across in my testing. Among these were

1. Fixed message forwarding. This was completely
broken when using IMAP.
2. Fixed the inability to save new messages as old
and vice versa.
3. Fixed the "delete" options in voicemail.conf when
using IMAP storage.

Even though a few bugs were fixed and the code is
a lot more consistent, the one thing that was *not*
improved in this branch was performance.

The merge of this to trunk may not come immediately
due to the amount of work it will probably involve.

(closes issue #12764)
Reported by: balsamcn

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@134223 65c4cc65-6c06-0410-ace0-fbb531ad65f3