* cygheap.h (cygheap_types): Add HEAP_ARCHETYPES.

(init_cheap::ctty): Change to pointer.
* dtable.h (dtable::find_archetype): Declare new function.
(dtable::add_archetype): Declare new function.
(dtable::delete_archetype): Declare new function.
(dtable::narchetypes): Declare.
(dtable::farchetypes): Declare.
(dtable::initial_archetype_size): Declare.
(dtable::dtable): Initialize new fields.
(dtable::initial_archetype_size): Declare.
* dtable.cc (dtable::find_archetype): Define new function.
(dtable::add_archetype): Define new function.
(dtable::delete_archetype): Define new function.
(dtable::initial_archetype_size): Define.
* fhandler.h (fhandler_base::archetype): Declare.
(fhandler_base::usecount): Declare.
* fhandler.cc (fhandler_base::fhandler_base): Initialize new fields.
* fhandler_console.cc (fhandler_console::get_tty_stuff): Pass NULL to third
argument of set_ctty.
* fhandler_tty.cc (fhandler_tty_slave::open): Accommodate new archetype method
to create only one instance of a tty.
(fhandler_tty_slave::close): Don't close handles unless archetype usecount is
zero.  When that happens, close archetype too.
(fhandler_tty_slave::dup): Just copy archetype.  Set use count appropriately.
Set ctty, if appropriate.
(fhandler_tty_common::dup): Remove slave considerations.
(fhandler_tty_common::set_close_on_exec): Remove cygheap->ctty considerations.
* pinfo.cc (_pinfo::set_ctty): Accommodate new archetype methods.
* pinfo.h (_pinfo::set_ctty): Make third argument explicit.
* syscalls.cc (close_all_files): Decrement controlling tty use count before
closing all handles to allow controlling tty to be closed.  Remove previous
controlling tty considerations.

winsup/cygwin/fhandler.cc

@@ -1177,7 +1177,9 @@ fhandler_base::fhandler_base ():
   rabuflen (0),
   open_status (0),
   fs_flags (0),
-  read_state (NULL)
+  read_state (NULL),
+  archetype (NULL),
+  usecount (0)
 {
 }