Sort Parser3 members by size and add consts

src/parser3.h

@@ -123,14 +123,14 @@ struct Parser3 {
   char *dataBegin;
   // Used for unescaping string data in place
   char *writeBuf;
-  const WeaselJsonCallbacks *const callbacks;
+  WeaselJsonCallbacks const *const callbacks;
   void *const userdata;
   Symbol *stackPtr;
-  bool complete;
   uint32_t utf8Codepoint;
   uint32_t utf16Surrogate;
   uint32_t minCodepoint;
-  int stackSize;
+  int const stackSize;
+  bool complete;
 };
 
 inline PRESERVE_NONE WeaselJsonStatus n_whitespace(Parser3 *self, char *buf,