Eliminate os.c and ApacheOS.dsp, ApacheOS.mak, et. al. Update the winnt

MPM to use native thread control calls rather than the deprecated stuff
in os.c. Even though I don't use APR in the MPM yet, this is forward
progress.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@84831 13f79535-47bb-0310-9956-ffa450edef68