Builtins and C++ and such

[Benjamin Kosnik]

> We have gotten this question more than once on the libstdc++ list; apparently
> there are people interested in using v3 with a compiler which is not GCC.

Non-issue. I've been assuming GCC-compatibile compiler all along. Note, 
this does not necessarily mean gcc, but something that implements all 
g++-isms used in the library. I think this is a safe assumption, and, 
from my past experience trying to make C++ library code fit into a 
multi-sized-and-compensating-for-weak-compiler hole in a past life, it's a 
smart one.

-benjamin