Fix bug #13735 with network streams on MS-Windows.

Fix bug #13735 with network streams on MS-Windows.
Revert changes to w32proc.c done since revision 111040.

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.