Merge r384731, r386790, r386821 from trunk.

    *  Unsure why win32 never noticed this, but the value returned is a const
       char*

    *  Escape from casting purgatory, which the Solaris cc compiler
       will not treat as lvalues.

    * Eliminate last win32-isms, SetLastError becomes apr's set_os_error
      operation.  It unfolds the error code on win32, so we have to pre-fold
      it.  On unix there is no folding.
    


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.0.x@395187 13f79535-47bb-0310-9956-ffa450edef68