Bug fixes large and small for tokenize.

Bug fixes large and small for tokenize.

Small: Always generate a NL or NEWLINE token following
       a COMMENT token.  The old code did not generate an NL token if
       the comment was on a line by itself.

Large: The output of untokenize() will now match the
       input exactly if it is passed the full token sequence.  The
       old, crufty output is still generated if a limited input
       sequence is provided, where limited means that it does not
       include position information for tokens.

Remaining bug: There is no CONTINUATION token (\) so there is no way
for untokenize() to handle such code.

Also, expanded the number of doctests in hopes of eventually removing
the old-style tests that compare against a golden file.

Bug fix candidate for Python 2.5.1. (Sigh.)