NAPI documentation

[Stephen Hemminger]

I took this opportunity to get a start on improving NAPI documentation.
I mashed together the short text about NAPI (with permission) from lwn.net
and the existing NAPI-HOWTO, to make a page on the Linux net wiki.

I took the liberty of removing some of the bits that were out of date, or referred
to old Becker code. It still needs lots of editing to be presentable.

Please edit and improve
	http://linux-net.osdl.org/index.php/NAPI

When the page is in good shape, I will de-wiki it to place in kernel doc tree.