More corpus.doctest fixes: less items returned by '.words()' methods, PTB 3.x fixes, corpora path fixes.
More corpus.doctest fixes: less items returned by '.words()' methods, PTB 3.x fixes, corpora path fixes.

The length of a AbstractLazySequence __repr__ becomes longer (because corpora is switched to unicode and __repr__ began to contain 'u' letters under 2.x) so it is truncated earlier than before - that's why the tests use smaller sequences.

nltk/nltk,nltk/nltk,nltk/nltk