Add a icon to the OSTC, Mk.2/2N config line

The icon comes from heinrichsweikamp.com, the same as the ostc3.png did.

I've emailed with Matthias Heinrichs at HW and they have given us
permission to use both the ostc3.png and ostc2n.png under the GPL v2.

They also can provide the hi-res originals if anyone needs to do more
work on these icons.

Signed-off-by: Anton Lundin <glance@acc.umu.se>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

qt-ui/configuredivecomputerdialog.ui

@@ -188,6 +188,10 @@
        <property name="text">
         <string>OSTC, Mk.2/2N/2C</string>
        </property>
+       <property name="icon">
+        <iconset resource="../subsurface.qrc">
+         <normaloff>:/icons/ostc2n.png</normaloff>:/icons/ostc2n.png</iconset>
+       </property>
       </item>
      </widget>
      <widget class="QStackedWidget" name="dcStackedWidget">

subsurface.qrc

@@ -65,6 +65,7 @@
         <file>icons/subsurface/32x32/actions/go-down.png</file>
         <file>icons/subsurface/32x32/actions/go-up.png</file>
         <file>icons/subsurface/32x32/actions/window-close.png</file>
+        <file>icons/ostc2n.png</file>
         <file>icons/ostc3.png</file>
         <file>icons/suunto_vyper.png</file>
     </qresource>