detecting supported opengl extensions

[almos]

Now that I checked the GLEW docs, I see that it is very easy to fix: the lines that say "if (!GL_extension_name)" should be changed to "if (!GLEW_extension_name)". Half of them are OK, the last 3 needs to be changed.

With this change vdrift says INFO: Your video card doesn't support floating point textures. Disabling shaders.
instead of crashing on FBO initialization, if one uses Mesa.

BTW are float textures and half float pixel really necessary for this game? It runs OK without shaders, so I assume the textures are not float initially, and all shaders seem to compile fine, if this check is omitted. I tried to change "format=RGBA16" to "format=RGBA8" in render.conf.deferred (the only place it is used), and it didn't issue an error (but the mesa shader compiler hit a hardware limitation on my ati rv350...)

AFAIK these extensions are only required by GL3.x, and AFAIK Mesa won't support them in the near future due to patent issues. I can't believe HDR and the other effects can't be implemented in GL2.1.

Also, your shader codes use texture2DLod() function without checking for GL_ARB_shader_texture_lod extension.