fix #K4172 - selling all into container

When using #loot to put items into a shop-owned container on a shop's
floor, you are asked "Sell it? [ynaq] (n)" for each item, but the 'a'
and 'q' choices only worked as y or n for the current item.  By the
next one, the preferred answer had been reset to default and ynaq was
asked again.

Set a flag in use_container() to have in_container() set the sell vs
don't sell state for the first item but not for any others.  Reset
the state at the end of use_container() instead of after each item in
in_container().

This bug was present in 3.6.x, also in 3.4.3, and probably earlier.

src/decl.c

@@ -1,4 +1,4 @@
-/* NetHack 3.7	decl.c	$NHDT-Date: 1706079841 2024/01/24 07:04:01 $  $NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.314 $ */
+/* NetHack 3.7	decl.c	$NHDT-Date: 1720074480 2024/07/04 06:28:00 $  $NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.334 $ */
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /*-Copyright (c) Michael Allison, 2009. */
 /* NetHack may be freely redistributed.  See license for details. */
@@ -792,6 +792,7 @@ static const struct instance_globals_s g_init_s = {
     (struct menucoloring *) 0, /* save_colorings */
     FALSE, /* simple_options_help */
     /* pickup.c */
+    FALSE, /* sellobj_first */
     FALSE, /* shop_filter */
     /* pline.c */
 #ifdef DUMPLOG_CORE