variable # of args portability?

[Wayne A. Christopher]

I want to be able to write a function that will take an unknown number
of arguments and then call another such function with these arguments,
namely something like printf() that calls _doprnt() without processing
its arguments at all.  I know there is no way to write this code portably,
but is it reasonable to assume that I will be able to do it at all in
most common implementations of C?  Also, how safe is it to assume that there
will be something like _doprnt() available?  I know it's not good to depend on
things like this, but I don't want to have to write my own printf()...

	Wayne