SPV: Implement Vulkan 1.1 features and extensions.

Test/spv.subgroup.vert

@@ -0,0 +1,11 @@
+#version 450
+#extension GL_KHR_shader_subgroup_basic: enable
+layout(set = 0, binding = 0, std430) buffer Output
+{
+  uvec4 result[];
+};
+
+void main (void)
+{
+  result[gl_VertexIndex] = uvec4(gl_SubgroupSize, gl_SubgroupInvocationID, 0, 0);
+}