Win32: Eliminate blocking network i/o in the Windows code paths. In practice

Win32: Eliminate blocking network i/o in the Windows code paths. In practice
only sends() were ever blocking. That any network i/o was ever blocking
could be considered a bug in Apache.

This patch seems to work around a bug in WinXP that causes network write
data corruption. The bug appears to be tickled by the combined use of
WSADuplicateSocket and blocking sends().  Allan Edwards is submitting a
bug report to Microsoft.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@93353 13f79535-47bb-0310-9956-ffa450edef68