Fix issue related to pointer storage. (#86)

Change type of `ci` in pointer value to `int` for an explicit signed type, since `char` is sometimes (e.g. emscripten) unsigned.

inkcpp/value.h

@@ -213,7 +213,7 @@ class value : public snapshot_interface
 
 		struct {
 			hash_t name;
-			char   ci;
+			int    ci;
 		} pointer;
 	};