Implement some GPU features (#209)

* Implement stencil testing

* Implement depth testing

* Implement face culling

* Implement front face

* Comparison functions now take OGL enums too

* Fix front facing when flipping was used

* Add depth and stencil clear values

Ryujinx.Graphics/Gal/GalStencilOp.cs

@@ -0,0 +1,14 @@
+namespace Ryujinx.Graphics.Gal
+{
+    public enum GalStencilOp
+    {
+        Keep     = 0x1,
+        Zero     = 0x2,
+        Replace  = 0x3,
+        Incr     = 0x4,
+        Decr     = 0x5,
+        Invert   = 0x6,
+        IncrWrap = 0x7,
+        DecrWrap = 0x8
+    }
+}