- When doing variable substitutions, you can omit the section name to
  refer to a variable in the same section (e.g. ${:foo}).

- When doing variable substitution, you can use the special option,
  ``_buildout_section_name_`` to get the section name.  This is most handy
  for getting the current section name (e.g. ${:_buildout_section_name_}).

- A new special option, ``<`` allows sections to be used as macros.