[Patch] Fix ac_c99_complex configury

[Paolo Carlini]

Mark Mitchell wrote:

> Heh.  Do you actually know the answer to my question, or are you
> confused like me?

I don't, really, on the spot: otherwise I would have insisted with
Benjamin (right now I'm absorbed by move semantics, by the way): I can
*see* that configure.ac is clearly split in two parts, and a working
linker is *not* assumed for crosses. Honestly, I have *no* idea why: I
don't build cross-compilers very often myself, admittedly. Can you
figure out something more by looking at configure.ac?!? I would really
like to learn more about all that.

Speaking of questions: what about my question regarding
include/backward? Are your customers still including <iostream.h>? Tell
me not ;)

Paolo.