dir.c: enumm answer

* dir.c (enumm answer): remap NO and YES to false and true,
  respectively.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@36901 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

dir.c

@@ -1260,7 +1260,7 @@ join_path(const char *path, int dirsep, const char *name)
     return buf;
 }
 
-enum answer { YES, NO, UNKNOWN };
+enum answer {UNKNOWN = -1, NO, YES};
 
 #ifndef S_ISDIR
 #   define S_ISDIR(m) (((m) & S_IFMT) == S_IFDIR)