Added stencil test to camera features.

src/Camera.h

@@ -50,6 +50,7 @@ class MAGNUM_EXPORT Camera: public Object {
             DepthClamp = GL_DEPTH_CLAMP,
 
             DepthTest = GL_DEPTH_TEST,      /**< Depth test */
+            StencilTest = GL_STENCIL_TEST,  /**< Stencil test */
             Dithering = GL_DITHER,          /**< Dithering (enabled by default) */
             FaceCulling = GL_CULL_FACE      /**< Back face culling */
         };