Implement Geometry shaders (#280)

* Implement Geometry shaders

* Add EmitVertex() and EndPrimitive()

* Read output geometry data from header

* Stub Vmad

* Add Iadd_I32

* Stub Mov_S (S2R)

* Stub Isberd

* Change vertex index to gpr39 in Abuf

* Add stub messages for consistency

* Do not print input block when there is no attributes

* Use GL_ARB_enhanced_layouts

* Skip geometry shaders when there's no GL_ARB_enhanced_layouts

* Address feedback

* Address feedback

Ryujinx.Graphics/Gal/Shader/ShaderIrInst.cs

@@ -82,6 +82,9 @@ namespace Ryujinx.Graphics.Gal.Shader
 
         Bra,
         Exit,
-        Kil
+        Kil,
+        
+        Emit,
+        Cut
     }
 }