support linenoise in mirb

I would like to linenoise instead of readline in mirb.

We can use linenoise in the following steps if this pr is merged.

- download linenoise from https://github.com/antirez/linenoise
- $ cp linenoise.h include/
- $ cp linenoise.c src/
- $ make CFLAGS="-DENABLE_LINENOISE"