g++ compile-time regression

[Joe Buck]

> <<3.1 is ten times slower than 2.95.1 for a 'hello world' program :).
> >>
> 
> Well hello world is hardly an interesting example, so this data point alone
> is not something to get too worried about.

I suspect that the slowdown is caused mainly by the much more complicated
libstdc++-v3 ... it takes longer to parse those headers.  This complexity
is unavoidable if we want to be standards conformant: in the old library,
ostream wasn't a template.

Still, anything that lets us parse those headers faster would be a win.