renattach 1.2.1

This latest version brings a number of new features, the most important of
which is the ability to search for filenames inside ZIP archives. This is
accomplished using an efficient technique that allows scanning on the fly,
without calling external programs or extracting the ZIP contents.

There is also an important security fix in version 1.2.1 that concerns the
--pipe feature (used for MTA integration); shell characters are now stripped
from the external pipe command line to guard against embedded commands.
