C++11 alignof alignas testcase and further C++11 doc updates

Examples/test-suite/cpp11_alignment.i

@@ -0,0 +1,16 @@
+%module cpp11_alignment
+
+%inline %{
+struct A {
+  int member;
+};
+const int align1 = alignof(A::member);
+%}
+
+%{
+// alignas - not yet working
+struct alignas(16) S {
+  int num;
+};
+alignas(double) unsigned char c[sizeof(double)];
+%}