Include ctype.h for isdigit().

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@2555 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ext/dl/dl.c

@@ -4,6 +4,7 @@
 
 #include <ruby.h>
 #include <rubyio.h>
+#include <ctype.h>
 #include "dl.h"
 
 VALUE rb_mDL;