jai-like CTFE string formating

[Stefan Koch via Digitalmars-d]

Hi Guys,

I've just implemented a subset of the std.format functionality.
In the same style that Johnathan Blow uses for JAI.

It's about 10x faster then using std.format and uses much less 
memory :)

the follwing code takes over 250 ms to compile :
{
     import std.format;
     pragma(msg, format("Hello %s %s %s %s %s %s %s %s %s", " I ", 
  "just", " have", " to", " concat",  " a lot", " of", " strings 
...", 9));
}
Whereas the following alternative takes 20 ms :
{
     import ctfe_utils;
     pragma(msg, format_jai("Hello % % % % % % % % %", " I ", " 
just", " have" , " to", " concat", " a lot", " of", " strings 
...", 9));
}

see for yourself:
https://www.youtube.com/watch?v=T0BJxdt61RY