Function gl::CopyTexSubImage2D

pub unsafe fn CopyTexSubImage2D(
    target: GLenum, 
    level: GLint, 
    xoffset: GLint, 
    yoffset: GLint, 
    x: GLint, 
    y: GLint, 
    width: GLsizei, 
    height: GLsizei
)

Fallbacks: CopyTexSubImage2DEXT