I'm hesitant to see this fix really works, except that I wrote a very
minimal test suite that covers all the cases I'm aware of.  The
previous checkin caused numberic operations when the Missing object
was on the right-hand side.

with new Zope3 interfaces

Fixes crash reported by Tres Seaver.  Missing.Value offered to coerce
itself to unicode.  unicode_compare() blew up because it expected that
the other argument had been converted to unicode.

XXX But why does this implement coercion at all?

  - Do what the docstring says:

    If -i is specified or no action is specified on the command line, a
    "shell" interpreting actions typed interactively is started.

Port multiple selection property fix from 2.6 branch. Also undid a previous fix which prevented multiple select properties from being added TTW.

addressed, so I just improved encodeExpansion()'s compression behavior.

specifically set.

selection" properties better (ie. default to an empty list, not empty string)

- normalize whitespace

  it more readable
- remove unused instance variable

PageTemplateFile.__init__() does some weird magic.
Without this, the sniffer tests failed on Windows.

- modernize a type-check

- modernize several type-checks
- remove unused imports

referenced for too long.

case if we're aborting e.g. a transactional undo.

You never need an __del__ to close a file.  A file closes itself when
it is deallocated.

Don't give an object a magic __del__ attribute.  It won't work with
new-style classes, and it's obscure anyway.