dri: Add a CriticalErrorMessageF macro.

dri: Add a CriticalErrorMessageF macro.

Sometimes an error is so sever that we want to print it even when the
user hasn't specifically requested debugging by setting LIBGL_DEBUG.

Add a CriticalErrorMessageF macro to be used for this case. (The error
message can still be slienced with the existing LIBGL_DEBUG=quiet).

For critical error messages we also direct the user to set the
LIBGL_DEBUG environment variable for more details.

Reviewed-by: Eugeni Dodonov <eugeni.dodonov@intel.com>