back-port this from 2.1-dev:

  Unix MPMs: Stop dropping connections when the file descriptor
  is at least FD_SETSIZE.

Submitted by:	trawick
Reviewed by:	nd, jorton


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/APACHE_2_0_BRANCH@103777 13f79535-47bb-0310-9956-ffa450edef68