Alien Ruin fix, various cherrypicked upstream fixes

Also adds new buildmode

code/modules/buildmode/submodes/copy.dm

@@ -0,0 +1,28 @@
+/datum/buildmode_mode/copy
+	key = "copy"
+	var/atom/movable/stored = null
+
+/datum/buildmode_mode/copy/Destroy()
+	stored = null
+	return ..()
+
+/datum/buildmode_mode/copy/show_help(client/c)
+	to_chat(c, "<span class='notice'>***********************************************************</span>")
+	to_chat(c, "<span class='notice'>Left Mouse Button on obj/turf/mob   = Spawn a Copy of selected target</span>")
+	to_chat(c, "<span class='notice'>Right Mouse Button on obj/mob = Select target to copy</span>")
+	to_chat(c, "<span class='notice'>***********************************************************</span>")
+
+/datum/buildmode_mode/copy/handle_click(client/c, params, obj/object)
+	var/list/pa = params2list(params)
+	var/left_click = pa.Find("left")
+	var/right_click = pa.Find("right")
+
+	if(left_click)
+		var/turf/T = get_turf(object)
+		if(stored)
+			DuplicateObject(stored, perfectcopy=1, sameloc=0,newloc=T)
+			log_admin("Build Mode: [key_name(c)] copied [stored] to [AREACOORD(object)]")
+	else if(right_click)
+		if(ismovableatom(object)) // No copying turfs for now.
+			to_chat(c, "<span class='notice'>[object] set as template.</span>")
+			stored = object