[PATCH] Add install-html stub for libstdc++-v3

[Benjamin Kosnik]

> +# Install distribution html documentation, doxygen documentation
> +# also needs install.
> +
> +.PHONY: install-html
> +
> +install-html:

Hmm. Well, this does nothing. 

What are you trying to do?

I see an "install-html" rule in libiberty. If you're going to do
something similar, I'd rather it do something, like what the comment
says. (Ie, install the docs, generate and install the doxygen bits.)

Sound reasonable?

-benjamin