Cleaned up the testing for the OpenGL libraries and headers and made the testing process a little smarter.  If available, the X11 header path is included when looking for GL/gl.h which provides a fallback to the X installation as a possible location for the OpenGL stuff.  The test for GL/gl.h is now separated (in the code) from the test for libGL so that this fallback can be implemented properly.  A great deal of redundancy has been removed in the path settings.  $LDFLAGS is always used in paths, so we use it for augmenting the library path rather than putting in "-L${OGLROOT}/lib" here and there.  It works out a lot better this way.
Cleaned up the testing for the OpenGL libraries and headers and made the
testing process a little smarter.  If available, the X11 header path is
included when looking for GL/gl.h which provides a fallback to the X
installation as a possible location for the OpenGL stuff.  The test for
GL/gl.h is now separated (in the code) from the test for libGL so that this
fallback can be implemented properly.  A great deal of redundancy has been
removed in the path settings.  $LDFLAGS is always used in paths, so we use
it for augmenting the library path rather than putting in
"-L${OGLROOT}/lib" here and there.  It works out a lot better this way.


git-svn-id: 769d22dfa2d22aad706b9a451492fb87c0735f19@1739 08b38cba-cd3b-11de-854e-f91c5b6e4272

vrjuggler/vrjuggler,vrjuggler/vrjuggler,MichaelMcDonnell/vrjuggler,godbyk/vrjuggler-upstream-old,vancegroup-mirrors/vrjuggler,vrjuggler/vrjuggler,LiuKeHua/vrjuggler,vancegroup-mirrors/vrjuggler,godbyk/vrjuggler-upstream-old,MichaelMcDonnell/vrjuggler,MichaelMcDonnell/vrjuggler,godbyk/vrjuggler-upstream-old,godbyk/vrjuggler-upstream-old,LiuKeHua/vrjuggler,LiuKeHua/vrjuggler,vancegroup-mirrors/vrjuggler,MichaelMcDonnell/vrjuggler,vrjuggler/vrjuggler,vrjuggler/vrjuggler,MichaelMcDonnell/vrjuggler,vrjuggler/vrjuggler,vancegroup-mirrors/vrjuggler,MichaelMcDonnell/vrjuggler,LiuKeHua/vrjuggler,vrjuggler/vrjuggler,godbyk/vrjuggler-upstream-old,vrjuggler/vrjuggler,vancegroup-mirrors/vrjuggler,LiuKeHua/vrjuggler,MichaelMcDonnell/vrjuggler,MichaelMcDonnell/vrjuggler,LiuKeHua/vrjuggler,godbyk/vrjuggler-upstream-old,LiuKeHua/vrjuggler,vancegroup-mirrors/vrjuggler,LiuKeHua/vrjuggler