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.frag

@@ -0,0 +1,7 @@
+#version 450
+#extension GL_NV_shader_sm_builtins: enable
+layout(location = 0) out uvec4 data;
+void main (void)
+{
+  data = uvec4(gl_WarpsPerSMNV, gl_SMCountNV, gl_WarpIDNV, gl_SMIDNV);
+}