Improve GL error report messages

[ben-clayton]

We still have nonsense being displayed for GL errors. We need to fix this.
Example: Invalid value "value" for "variable"

[dsrbecky]

My vote is that it is more important to get all the GL errors in pace first, rather make the code more complex by adding the custom error messages for a few. So I would just drop the text if it does not make sense, or just drop all the texts for now.

Let's do the simple thing first, and do the complex solution later please?

[dsrbecky]

We could provide the URL for the online help for the given command - that should make it possible for the user to lookup what caused the error. It is not ideal, but it is simple to start with.

[dsrbecky]

Also note that drivers can provide string messages together with the errors. Maybe we should use those for now?

[ben-clayton]

I'm fine with removing the variable names from the message as a first step - that would lower the priority to p3.

[dsrbecky]

That should probably work - I will take a look.

[ben-clayton]

Thanks!

[dsrbecky]

#885