Small refactoring regarding symbols for clarity.

include/mrbconf.h

@@ -150,7 +150,7 @@
 
 /* -DMRB_USE_XXXX to enable following features */
 //#define MRB_USE_DEBUG_HOOK /* hooks for debugger */
-//#define MRB_USE_ALL_SYMBOLS /* Symbols.all_symbols */
+//#define MRB_USE_ALL_SYMBOLS /* Symbol.all_symbols */
 
 /* obsolete configurations */
 #if defined(DISABLE_STDIO) || defined(MRB_DISABLE_STDIO)

src/symbol.c

@@ -73,7 +73,7 @@ typedef struct symbol_name {
 static void
 sym_validate_len(mrb_state *mrb, size_t len)
 {
-  if (len >= RITE_LV_NULL_MARK) {
+  if (len >= UINT16_MAX) {
     mrb_raise(mrb, E_ARGUMENT_ERROR, "symbol length too long");
   }
 }