run-tests: fix heredoctest for out-of-tree extensions
heredoctest.py directory must be in python path to use heredoctest (>>>) in
out-of-tree extension tests like:
$ cd ext/tests
$ python /some/hg/install/tests/run-tests.py test-ext.t
[ original upstream message ]
# $Id$
include tests/test-keyword tests/test-keyword.out
include MANIFEST.in