SimGear - Real time simulation tools

By compiling the current cvs sources on my G4 running Mac S X 10.4.4
the file RenderTexture.cpp does not compile because several OpenGL
function are not declared.

Including OpenGL/OpenGL.h within RenderTexture.h removes the errors
and simgear gets compiled.

Here are the diff reports:

cvs diff RenderTexture.h
Index: RenderTexture.h
=============================================
======================
RCS file: /var/cvs/SimGear-0.3/source/simgear/screen/
RenderTexture.h,v
retrieving revision 1.9
diff -r1.9 RenderTexture.h
57a58
> # include <OpenGL/OpenGL.h>