std.metastrings and Variadic CTFE funcs

[Bill Baxter]

To Don, Walter, or anyone else who knows:
How hard is it going to be to get variadic CTFE functions working?
Or how hard would it be to get

std.metastrings.Format should be a major workhorse of CTFE string
functions, but it can't be because it's all done using template args.
And I'm assuming it's a template because variadic CTFE funcs don't work.


In general, it would be nice to have more std.string functions
available (as CTFE-capable functions) in std.metastrings.  Like
Replace and IndexOf.  I whipped up a quick version of those two based
somewhat on std.strings' versions just now.

--bb