SHARED_LIBS status

[Marc Espie <espie_(_at_)_nerim_(_dot_)_net>]

We're now almost done converting all ports to SHARED_LIBS, and a huge
subset of them to USE_LIBTOOL instead of building their ports.

In the very near future (before tuesday, probably), pkg_create is going
to start erroring out if it finds shared libraries that are not under
SHARED_LIBS control.  I expect this to be under 25 packages at that point.

New ports HAVE to heed SHARED_LIBS. In most packages using libtool, it's
just a question of setting USE_LIBTOOL together with SHARED_LIBS.

The current conversion showed us that, in most cases, it's very easy to
do.