Treat partial hook success '\n' to fix #2361 .

Ignore outfile check when `-c`(check syntax only) flag is enabled.

Now it will parse the #2361 code as:
```
module A
end
module B
end
```
instead of
```
module A
end module B
end
```

Add generator script to dependency so that it will regenerate C codes when it's modified.

various mruby-struct function changes

Release `mrb->atexit_stack` on `mrb_close`.

Fix compilation fail caused by GNU Readline and `ISPRINT`.
Also add missing `unsigned char` cast.

`ISSPACE` and `ISASCII` can be used instead.