[Bug-zile] Adding Unicode support

[Garnaik Sumeet]

Hello Gary and Reuben Sir,

         I kind of overviewed the source of zile and hopefully I have figured it out on how to add unicode support to zile.

I believe the following files in the zile library will get really few changes,the code is really well structured and not much of it will get affected to add support for UTF-8.

/zile/bind.lua
/zile/buffer.lua
/zile/completion.lua
/zile/file.lua
/zile/keycode.lua
/zile/search.lua
/zile/term_curses.lua
/zile/term_minibuf.lua
/zile/term_redisplay.lua
/zile/window.lua
/zmacs/specs/spec_helper.lua
/zz/eval.lua

There a few libraries that provide support for unicode.....slnunicode(available in the luarocks repository)......but I also found another one

https://github.com/starwing/luautf8

Since the data structure in zile are mutable and lua performs all the operations in terms of bytes.....the only thing we need to care about in case of utf-8 is for functions that manipulate the strings and functions that display the chars on the screen(lcurses takes care of these since it uses alien to give a complete binding to the ncurses library).

Hopefully I have got a correct idea of the code base of zile.Eagerly awaiting for you feedback.

Thank you,

Sumeet Garnaik.