gcc 3.0 cannot compile pooma

[Benjamin Kosnik]

> It's not at all clear to me what the c_shadow headers are trying to do
> or why they don't work.  However, closing namespaces and extern "C"
> blocks at the _beginning_ of a header and opening them at the _end_
> looks, at the very least, impossibly fragile.

the extern "C" bits have to go. They add needless complexity: a patch 
that removed them (in both math.h and bits/std_cmath.h in the c_shadow 
directory) can be considered pre-approved.

The namespace trickery has to remain,  however.

> Nathan Meyers' description of the original shadow concept seemed a lot
> simpler and more likely to work properly, to me (I thought it was
> somewhere on cantrip.org but I can't find it anymore).

Hmm. Here's the URL:

http://www.cantrip.org/cheaders.html