set_forward_compatible
Description:
Sets whether the `GdkGLContext` should be forward-compatible.
Forward-compatible contexts must not support OpenGL functionality that has been marked as deprecated in the requested version; non-forward compatible contexts, on the other hand, must support both deprecated and non deprecated functionality.
The `GdkGLContext` must not be realized or made current prior to calling this function.
Parameters:
| this | 
           a `GdkGLContext`  | 
      
| compatible | 
           whether the context should be forward-compatible  |