Revision 83739

Use AcceptEx (a.k.a. accept and receive) on windows NT. Begin work to make
the WIN9x code co-exist with the NT specific code. Since I started this work,
I've managed to improve the static page serving performance of Apache on NT by
almost 50%. Still a long way from Apache on Linux though.

TODO:
- Reuse the AcceptEx accept socket (performance)
- Clean up the organization of the winnt mpm
- Implement Async AcceptEx and Receive. Will this break modules?
- File handle cache (file i/o accounts for more than 50% of the time per request)
- TransmitFile (I have prototype code implemented). Should we add a send_file API
to the I/O control layer? Maybe Apache should always try to send_file. Platforms
that don't support send_file could in turn, invoke the appropriate buff code
which would then invoke socket iol write/writev.