Partial libmutt upgrade

[Bruno Pires Marinho <bapm camoes rnl ist utl pt>]

Hi people.

I finally got the libmutt upgrade patch ready and I have just commited it
to CVS.

It was not ready Yesterday because I under estimated the work needed to
upgrade libmutt to the latest version. To see what I mean an unified diff of
the two versions has 180k lines! I'm not surprise when we have a libmutt
from 4 of September of 1998.

I have restricted my self to upgrade only the files on the Makefile.am and
the ones that really needed to be added (There is no problem because
the other files are used for the interface). This reduced the diff to 16k
lines. But some files must be looked at especially the ones related to
charsets (I will do this later).

Following more or less the diff and ChangeLog I found multiple bug fixes
including IMAP and new features like pgp (which can be activated later if
we want).

While putting togger this patch I did not forget the LIBMUTT entries
placed by Stuart (I'm guessing he put them there) and the ones placed by
David for the BALSA_THREADS (if I miss anything please let me know).

I tried the new version of libmutt but since I don't use POP (this means
also that I did not test the multi-thread code) or IMAP support I don't
know if it broke something or more importantly what is fixed!

This patch also changes some files other than the ones on libmutt but it
is because of little libmutt interface changes.

                                               Bruno Pires Marinho
                                      http://camoes.rnl.ist.utl.pt/~bapm/