[xboard 4.8] Naming and installation of xqwood/xqboard.png

Hello!


I noticed that

 * xqboard.png has not been renamed to xqboard-9x10.png
   so the rendering/theme using that image is still
   at the broken state of pre-4.8.

 * xqwood.png is only installed in OS X while
   it may be interesting to users of say Linux, too.
   xqwood.png should probably be renamed to xqwood-9x10.png
   for proper rendering, too.

Please let me know if I'm missing anything and if there's a chance to
have 4.8.1 with a fix some time soon.

Best,



Sebastian