urlizetrunc filter appending elipsis to uris of exactly the truncate length

[Chris Beaven]

>>> from django.template.defaultfilters import urlizetrunc
>>> uri = 'http://31characteruri.com/test/'
>>> len(uri)
31
>>> urlizetrunc(uri, 31)
'<a href="http://31characteruri.com/test/" rel="nofollow">http://31characteruri.com/test/...</a>'

The attached patch addresses this. Also, if the URI does need truncating, this patch changes it so that the truncation length is - 3 to adjust for the addition of the 3 elipsis characters (see the test in the patch for a better explanation).

[Chris Beaven]

with tests this time

[Malcolm Tredinnick]

(In [5513]) Fixed #4657 -- Fixed an error in an edge case of the urlizetrunc filter.
Thanks, SmileyChris.