whereby the identity of the "caller" callable
  inside the <%def> would be corrupted by the
  presence of another <%call> in the same block.
  [ticket:170]

  evaluates its contents in-place.
  Can be named or anonymous,
  the named version is intended for inheritance
  layouts where any given section can be
  surrounded by the <%block> tag in order for
  it to become overrideable by inheriting
  templates, without the need to specify a
  top-level <%def> plus explicit call.
  Modified scoping and argument rules as well as a
  more strictly enforced usage scheme make it ideal
  for this purpose without at all replacing most
  other things that defs are still good for.
  Lots of new docs. [ticket:164]

- convert heading copyrights to 2006-2011, reference AUTHORS file

  strict_undefined=True, will cause
  variables not found in the context to
  raise a NameError immediately, instead of
  defaulting to the UNDEFINED value.

  i.e. in place of cgi.escape().  Faster
  C-based implementation and also escapes
  single quotes for additional security.
  Supports the __html__ attribute for
  the given expression as well.

  When using "disable_unicode" mode,
  a pure Python HTML escaper function
  is used which also quotes single quotes.

  Note that Pylons by default doesn't
  use Mako's filter - check your
  environment.py file.

  uncommon feature, have been improved.  The defs
  no longer get doubly-rendered in the body() scope,
  and now allow local variable assignment without
  breakage.  [ticket:109]

  % if: %endif, etc. [ticket:94]
- finished cleanup for codegen.py, [ticket:98]

- Python 3 support is added ! See README.py3k
  for installation and testing notes.
  [ticket:119]