Add support for SPV_NV_geometry_shader_passthrough

Test/spv.GeometryShaderPassthrough.geom

@@ -0,0 +1,17 @@
+#version 450
+#extension GL_NV_geometry_shader_passthrough : require
+
+layout(triangles) in;
+
+layout(passthrough) in gl_PerVertex {
+    vec4 gl_Position;
+};
+
+layout(passthrough) in Inputs {
+vec2 texcoord;
+vec4 baseColor;
+};
+
+void main()
+{
+}