Fix bug #13735 with network streams on MS-Windows.
Revert changes to w32proc.c done since 2012-11-30T09:23:15Z!eliz@gnu.org.
Do NOT merge to trunk!
src/w32proc.c (new_child): Remove the loop that attempted to salvage
slots of dead processes.
(new_child, delete_child, find_child_pid): Don't insist on
procinfo.hProcess be NULL for a process slot to be considered
inactive, or be non-NULL to be considered active.
(reader_thread): Don't set the FILE_AT_EOF flag of a file
descriptor if the corresponding child was deleted and its
char_avail handle is NULL.
(reap_subprocess): Don't reset the FILE_AT_EOF flag.
(sys_select): Don't pass a NULL process handle to
WaitForMultipleObjects.
Fixes: debbugs:13735 debbugs:13546