[1.2.X] Fixed #11021 -- Clarified newline stripping behavior in the...

[1.2.X] Fixed #11021 -- Clarified newline stripping behavior in the truncatewords and truncatewords_html filters. Thanks to Ben Spaulding for the report and patch.

Backport of r13555 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@13562 bcc190cf-cafb-0310-a4f2-bffc1f526a37