HTML export: internal links broken

[Sebastian Rose <sebastian_rose@gmx.de>]

There is small bug in the XHTML export. Internal links point to nowhere.

* Example

*** In the orgfile:

    This [[Some Heading][Link]] should link to '*** Some Heading'.

*** After export, HTML file:

    This <a href="#Some--Heading">Link</a> should link to '*** Some
    Heading'.


There is no anchor defined with that name in the exported HTML. There
are two possibilities to change this:

    1) define the anchor next to the heading:
       <a id="Some--Heading" />

    2) If the link pionts to a heading, use the ID of the heading in the
       link: 
       ... <a href="sec-3.2.1">Link</a> to '*** Some Heading'.



The second one is the one I would prefer, but that would mean to handle
links to headings differently from links to user defined anchors. But it
would keep the nesting of section containers clean.


Regards,

   Sebastian