Add small OS/2 section with a link to further information.

patch by Dave Yeo, daveryeo telus net

Originally committed as revision 11186 to svn://svn.ffmpeg.org/ffmpeg/trunk

doc/general.texi

@@ -595,6 +595,11 @@ and for a build with shared libraries
 
 BeOS support is broken in mysterious ways.
 
+@section OS/2
+
+For information about compiling FFmpeg on OS/2 see
+@url{http://www.edm2.com/index.php/FFmpeg}.
+
 @chapter Developers Guide
 
 @section API