- Rephrased the description of the grammar, pointing out that the
  lexicon decides on globbing syntax.

- Refactored term and atom parsing (moving atom parsing into a
  separate method).  The previously checked-in version accidentally
  accepted some invalid forms like ``foo AND -bar''; this is fixed.

tests/testQueryParser.py:

- Each test is now in a separate method; this produces more output
  (alas) but makes pinpointing the errors much simpler.

- Added some tests catching ``foo AND -bar'' and similar.

- Added an explicit test class for the handling of stopwords.  The
  "and/" test no longer has to check self.__class__.

- Some refactoring of the TestQueryParser class; the utility methods
  are now in a base class TestQueryParserBase, in a different order;
  compareParseTrees() now shows the parse tree it got when raising an
  exception.  The parser is now self.parser instead of self.p (see
  below).

tests/testZCTextIndex.py:

- setUp() no longer needs to assign to self.p; the parser is
  consistently called self.parser now.