At least this now passes Evan's test_metal1.html!

I had to restructure attrAction() and the macroStack() quite a bit.
The macro stack now has a mostly abstract interface (a few lookups
still dig directly into the stack).

Weekend!

the test input filename contains the substring "metal".

quite easy to accidentally set off an infinite recursion here.

Remove unnecessary "global" statement -- already in global context.
Python 2.1 complained about this because the global was assigned to
before the global statement, all in a single scope.

dict of the raw attribute values.  Also, put beginScope/endScope
around each tag for which a tagDict is emitted, rather than only for
tags using define or repeat.  This affects the generated code, but
doesn't affect semantics (according to the tests).

tag.

- Define-slot can now be nested inside fill-slot, so that a macro can
  call another macro and use one of its slots to fill that other
  macro's slots.  (This is essential for sensible semantics of nested
  macros.)

- Inside a use-macro, if the macro defines a slot that's not filled,
  the define-slot turns into fill-slot.  (This is just a convenience
  feature.)

To implement this, the current macro call and its slots are turned
into a stack (they already had stack behavior but the stack was
inaccessible) and added a variable indicating the macro currently
being defined (if any).

In the process, refactored startTagCommon a bit, turning the decision
procedure for argument replacement into a separate method
(attrAction()).

Added a safeguard to the attribute-wrapping feature: if the alignment
column is too far to the right (half of the wrap column), change
alignment to 4 spaces.  This solves the problem reported by Gregor
Hoffleit with attribute wrapping in a long line containing several
elements.

that the issues remain to allowing unicode objects through Zope that are
not addressed herin, but are related to type('') not equalling type(u''); much
special case code exists that handles strings differently that needs
review to handle unicode as well.

after changes applied; tutorial functional with gadfly.

in setLocal() was improperly indented.

Evan: please, Please, PLEASE, run the test suite before checking in
changes!

__*attr__ magic methods don't work when you add them after the class is defined, so add them during class definition.

Implemented alternate path '|' operator.
Added 'default' builtin.
Made Expression types available to python expressions as functions.
Changed the way render() calls DTML.

Change WebDAV traversal to only turn off acquisition on the final traversal step.  This prevents a conflict with VirtualHostMonster.