Change h_heading to also scan toc title

[torik42]

This is the continuation of #196 after the transfer. Old discussion:

@torik42:

So far only the directly printed title of the commands \section and similar are checked. It would be nice if also the title for the table of contents given as an optional argument, i.e. \section[Short Title]{Long Title} would be checked.

My suggestion is to put it in the output as is done for the usual title, i.e. \section[a]{b} would be parsed as a. b. . The whitespace in the end even has the advantage that \section{Title}Some text will not yield a mistake any more.

Since there are a lot of tests, I did not adapt them yet. If you agree to the proposed changes, @matze-dd, I could do so.

@torik42:

One could maybe even make the addition of the dot a function by its own. This would make it easier to use it in other packages as well. I will need a similar thing in the beamer class, for example.

Something like

def append_dot(parser, toks):
    txt = parser.get_text_expanded(toks).strip()
    if (txt and parser.parms.heading_punct
            and txt[-1] not in parser.parms.heading_punct):
        toks.append(TextToken(toks[-1].pos, '.'))
    toks.append(SpaceToken(toks[-1].pos, ' '))