Fixed compilation error of "mruby-pack" with `MRB_NO_STDIO`
#define INT_OVERFLOW_P(n) ((n) < MRB_INT_MIN || (n) > MRB_INT_MAX)
#define UINT_OVERFLOW_P(n) ((n) > MRB_INT_MAX)
+#ifndef EOF
+# define EOF (-1) /* for MRB_NO_STDIO */
+#endif
+
struct tmpl {
mrb_value str;
int idx;
