[O] new exporter: link abbrev

[Michael Brand]

Hi all

I think the new exporter should still expand link abbreviations also
when in the heading and for all backends. Example with html link on
today’s release_7.9.2-646-g664217:

- Org file:
  #+LINK: orgmode http://www.orgmode.org/
  * Org Mode doc [[orgmode:#docs]]

- export to html:
  - old exporter expands link:
    <h2 id="sec-1"><span class="section-number-2">1</span> Org Mode doc
    <a href="http://www.orgmode.org/#docs";>http://www.orgmode.org/#docs</a></h2>
  - new exporter leaves link abbreviated:
    <h2 id="sec-1"><span class="section-number-2">1</span> Org Mode doc
    <i>orgmode:#docs</i></h2>

- export to ascii:
  - old exporter expands link:
    1 Org Mode doc [http://www.orgmode.org/#docs]
  - new exporter omits link:
    1 Org Mode doc

Michael