Eliminate C++11 from constant_expr test

This was introduced by a recent commit adding a testcase matching
an example in the manual.  There doesn't seem to be a suitable
termplate in the standard library before C++11, so instead use
a dummy version of std::array defined in the testcase.

Examples/test-suite/constant_expr.i

@@ -23,8 +23,15 @@ isPointer = false
 int a;
 int test2(int b = 9%a) { return b; }
 
-/* Example from manual. */
-#include <array>
-void bar(std::array<int, (1<2? 100 : 50)> *x) { }
+/* Example from manual, adapted to avoid C++11 requirement. */
+namespace fakestd {
+  template<typename T, unsigned N>
+  class array {
+      T a[N];
+    public:
+      array() {}
+  };
+}
+void bar(fakestd::array<int, (1<2? 100 : 50)> *x) { }
 
 %}