[OCaml] Fix the wrapping of static const member chars

OCaml's constantWrapper() was adding unneeded quotes when wrapping
static const member chars.

Add runtime tests for char_constant, chartest, and
static_const_member.

Examples/test-suite/ocaml/static_const_member_runme.ml

@@ -0,0 +1,9 @@
+open Swig
+open Static_const_member
+
+let _ =
+  assert (_X_PN '() as int = 0);
+  assert (_X_CN '() as int = 1);
+  assert (_X_EN '() as int = 2);
+  assert (_X_CHARTEST '() as char = 'A');
+;;