[R] Building RGL for R-2.3 for Tiger 10.4.6 on PPC

[Saptarshi Guha]

Hi,
	I just installed R-2.3 for Tiger 10.4.6 on a PPC. However, though i  
successfully installed RGL on R.2.2, this time it doesn't compile.
	I get this error when trying the R INSTALL command

	In file included from Texture.hpp:14,
                  from Material.hpp:5,
                  from BBoxDeco.hpp:16,
                  from BBoxDeco.cpp:1:
	opengl.hpp:22:19: error: GL/gl.h: No such file or directory
	opengl.hpp:23:20: error: GL/glu.h: No such file or directory
	make: *** [BBoxDeco.o] Error 1

	I'm not sure whats happening... my cocoa apps (some of which use  
OpenGL) compile successfully.

	Thanks for your time.
	Rgds
	Saptarshi