[OCaml] Runtime tests for constructor_rename, cpp_nodefault and some others

Add runtime tests for constructor_rename, cpp_nodefault, extend,
extend_special_variables, extend_template, extern_c, and
global_ns_arg.

Examples/test-suite/ocaml/extend_template_runme.ml

@@ -0,0 +1,8 @@
+open Swig
+open Extend_template
+
+let f = new_Foo_0 '()
+let _ =
+  assert((f -> "test1" (37) as int) = 37);
+  assert((f -> "test2" (42) as int) = 42);
+;;