add pickup_thrown option (trunk only)

This patch by <email deleted> was released
when 3.4.1 was current and has been incorporated into slash'em.  It is
extremely useful while using ranged weapons.  When both autopickup and
pickup_thrown are enabled, walking across previously thrown objects will
pick them up even if they don't match the current pickup_types list.
[See cvs log for patchlevel.h for longer description.]

src/dothrow.c

@@ -923,6 +923,7 @@ boolean twoweap; /* used to restore twoweapon mode if wielded weapon returns */
 	}
 
 	thrownobj = obj;
+	thrownobj->was_thrown = 1;
 
 	if(u.uswallow) {
 		mon = u.ustuck;