fix an off-by-one error.

mrbgems/generator.c

@@ -60,8 +60,9 @@ static char
  *     String which will be the replacement
  *
  */
-static char
-*replace(const char *s, const char *old, const char *new)
+
+static char *
+replace(const char *s, const char *old, const char *new)
 {
   char *ret;
   int i, count = 0;
@@ -75,7 +76,7 @@ static char
     }
   }
 
-  ret = malloc(i + count * (newlen - oldlen));
+  ret = malloc(i + count * (newlen - oldlen) + 1);
   if (ret == NULL)
     exit(EXIT_FAILURE);