On Win32 it is not valid to check whether the socket descriptor is

less than FD_SETSIZE.

Also, in http_main.c check that listenmaxfd is not -1 (which would
indicate that no sockets are available, and causes select() to fail
rather badly, i.e. it does not set a valid errno). Instead we should exit.
Add some more comments about how child/parent signalling works.

Fixup a couple of incorrect calls to the child_exit_modules before
child_init_modules had been called (this would only occur in a couple of
rare error conditions).


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@80651 13f79535-47bb-0310-9956-ffa450edef68