[imp] automatic name expansion for RELENG3

[Liam Hoekenga]

hey guys -

I've backported the auto-name expansion stuff to IMP 3.1.  It seems to be
working just fine.  The main thing involved was moving to functions out of
horde/imp/compose.php to horde/lib/MIME.php and horde/imp/lib/IMP.php.  The code
writen for CVS worked just fine with the IMP 3.1 versions of the equivalent
functions.

The patch can be found at:

http://www.umich.edu/~liamr/horde/auto_expand-RELENG3.diff

Liam