[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/char_constant_runme.ml

@@ -0,0 +1,16 @@
+open Swig
+open Char_constant
+
+let _ =
+  assert (_CHAR_CONSTANT '() as char = 'x');
+  assert (_STRING_CONSTANT '() as string = "xyzzy");
+  assert (_ESC_CONST '() as char = '\x01');
+  assert (_NULL_CONST '() as char = '\x00');
+  assert (_SPECIALCHARA '() as char = 'A');
+  assert (_SPECIALCHARB '() as char = 'B');
+  assert (_SPECIALCHARC '() as char = 'C');
+  assert (_SPECIALCHARD '() as char = 'D');
+  assert (_SPECIALCHARE '() as char = 'E');
+  assert (_ia '() as char = 'a');
+  assert (_ib '() as char = 'b');
+;;