Add support for GL_NV_shader_sm_builtins

Including spirv and AST tests

Also increase size of TBuiltInVariable bitfields since we've now exceeded 127
and add a static_assert to make this easier to find next time it happens!

Test/spv.smBuiltins.vert

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