Add UTF-8 support: ustring.lua ustring provided string-like APIs(eg. gsub,len,match) to support UTF-8 in pure lua(jit).
Add UTF-8 support: ustring.lua
ustring provided string-like APIs(eg. gsub,len,match) to support UTF-8 in pure lua(jit).

zhaozg/luvit,luvit/luvit,luvit/luvit,zhaozg/luvit