Revert "opengl32: Return a NULL pointer for functions requiring unsupported or disabled extensions.".

[Henri Verbeet]

On 27 November 2015 at 08:18, Sebastian Lackner <sebastian at fds-team.de> wrote:
> @Henri: Thanks for the explanation about the difference of wglGetProcAddress
> and glXGetProcAddress, I wasn't aware that the Windows version works more
> reliable, which explains why you would like to keep this part. Do you see
> any other chance to implement a more general detection which functions are
> available, than to rely on the extension string? Analyzing thunk wrappers,
> or doing a test call with exception handler would probably work, but sounds
> a bit too ugly. :/
>
Nothing that's reliable. E.g. that a function doesn't crash when you
call it doesn't mean it will actually work. And in the general case
you would somehow need to construct a set of valid parameters.