[bug-mailutils] Moving protocol support to a separate directory.

[Sergey Poznyakoff]

Hello,

I am going to move all low-level protocol support libraries (mbox, mh,
pop, etc.) from mailbox/ to a separate directory libproto/. This allows
to properly set up interlibrary dependencies. Eg. libmu_pop depends on
libmailutils and libmuath, which in turn depends on libmailutils, so the
proper build order is: (1) libmailbox, (2) libmuauth, (3) libmu_pop,
which cannot be achieved now, given that POP sources are located in a
subdirectory of mailbox/.

Any objections?

The test tarball using the new directory structure is available from:

 ftp://download.gnu.org.ua/pub/alpha/mailutils/mailutils-20060302.tar.bz2

Regards,
Sergey