Improve constants handling

Handle char constants defined using #define or %constant correctly.

Also handle static member const variables, which didn't work at all
before, and quote values of such variables of char type.

Source/Modules/c.cxx

@@ -1522,7 +1522,32 @@ public:
 
   virtual int constantWrapper(Node *n) {
     String *name = Getattr(n, "sym:name");
-    String *value = Getattr(n, "value");
+    // If it's a #define or a %constant, use raw value and hope that it will work in C as well as in C++. This is not ideal, but using "value" is even worse, as
+    // it doesn't even work for simple char constants such as "#define MY_X 'x'", that would end up unquoted in the generated code.
+    String *value = Getattr(n, "rawval");
+
+    if (!value) {
+      // Check if it's not a static member variable because its "value" is a reference to a C++ variable and won't translate to C correctly.
+      //
+      // Arguably, those should be handled in overridden memberconstantHandler() and not here.
+      value = Getattr(n, "staticmembervariableHandler:value");
+      if (value && Equal(Getattr(n, "valuetype"), "char")) {
+	// We need to quote this value.
+	const unsigned char c = *Char(value);
+	Clear(value);
+	if (isalnum(c)) {
+	  Printf(value, "'%c'", c);
+	} else {
+	  Printf(value, "'\\x%x%x'", c / 0x10, c % 0x10);
+	}
+      }
+    }
+
+    if (!value) {
+      // Fall back on whatever SWIG parsed the value as for all the rest.
+      value = Getattr(n, "value");
+    }
+
     Printv(f_wrappers_decl, "#define ", name, " ", value, "\n", NIL);
     return SWIG_OK;
   }