get_version

Description:

public void get_version (out int major, out int minor)

Retrieves the OpenGL version of the this.

The this must be realized prior to calling this function.

If the this has never been made current, the version cannot be known and it will return 0 for both major and minor.

this	a `GdkGLContext`
major	return location for the major version
minor	return location for the minor version