RFE: add libffi to LSB

[Jeff Johnson]

This bug is split out from bug 3548 - Add GTK+ 3 for LSB 5.0

It seemed that the gtk stack requires this library, and patches in bug 3548
have actually added it.

Now it's not so clear the library is needed for user code, and there's version
skew between distributions, where some have an soname of .4 and some of .5.

This bug is to track the status of libffi.

At the moment it's proposed to turn it back off, but leave the data in the
database for possible re-enablement, and certainly to support Navigator
queries. This bug should track the status of the library through the LSB 5.0
release.

I guess, without testing:

SET @Lid=(SELECT Lid FROM Library WHERE Lname='libffi');
UPDATE ArchLib SET ALappearedin='' WHERE ALlid=@Lid;