[libstdc++ patch] tr1::bind, take 2

[Benjamin Kosnik]

> In mainline, Steven already committed a nice compiler speed-up. Seems
> safe, and I will support as much as I can its backport to 4.0.1.

Oh! Ok. I didn't realize this was in mainline already. I'll have to
update. The timings I gave were for circa Sunday compiler sources.

> About pchs, adding tr1 bits it's possible, and would fix the make-check
> slow-down. Seems also easy to implement as a very tiny follow-up to
> Doug/Chris patch. However, as mentioned by Chris some time ago, the tr1
> pch header is rather big (at the time ~50 M). I'm not sure we want to
> increase the size of the pch for the sake of the tr1 users... What do
> you think?

Hmmmmm. 50MB is kinda big, agreed. The current stdc++ PCH is about 19MB. 

We could do a tr1.h.pch for the build directory only. That would give us
the make check speedup.

That might be more special casing and build hacking than is useful though.

Dunno.

-benjamin