Fix the call to StencilFuncSeparate for gl::FRONT.
Fix the call to StencilFuncSeparate for gl::FRONT.

While the state was tracked correctly, the settings for gl::BACK
were applied instead.

caldwell/glium,carbidegames/glium,sdotz/glium,acolley/glium,glium/glium,nicokoch/glium,cpjreynolds/glium,tomaka/glium