support SPV_NV_viewport_array2 and SPV_NV_stereo_view_rendering

Test/spv.stereoViewRendering.tesc

@@ -0,0 +1,18 @@
+#version 450
+
+#extension GL_NV_viewport_array2 :require
+#extension GL_NV_stereo_view_rendering : require
+
+layout(vertices = 4) out;
+
+out gl_PerVertex {
+    int gl_SecondaryViewportMaskNV[2];
+    vec4 gl_SecondaryPositionNV;
+    layout (viewport_relative, secondary_view_offset = 1) out highp int gl_Layer;
+} gl_out[4];
+
+void main()
+{
+    gl_out[gl_InvocationID].gl_SecondaryViewportMaskNV[0]            = 1;
+    gl_out[gl_InvocationID].gl_SecondaryPositionNV                   = gl_in[1].gl_Position;
+}