[opengl] Catch BadMatch errors before they can occur.

[Tomas Carnecky]

Lionel Ulmer wrote:
>> Oh, and this patch creates a new debug-channel 'swapbuffers' and puts
>> both opengl swapbuffers functions into it.
> 
> What is the reason for this change ?
> 

When debugging opengl applications, I'm usually not interested in the
*Swap*Buffers() functions, but in context creation, pbuffers stuff etc.
It just writes unnecessary messages into the console. When debugging an
application that crashes after 10 minutes it makes the log very big. If
someone is interested in the *Swap*Buffers() functions, he still can
enable them, but for the majority of the cases its useless.

That was basically the idea. I'll rewrite the patch and split it up, the
GLX spec violation thing could be committed without breaking
applications, other changes have to be tested first :)

tom