Fix for disposal pipes not vanishing under floors.

This is a fix for issue #291. Disposals pipes should now properly stop
displaying when a floor is placed on top of them.

code/modules/recycling/disposal-construction.dm

@@ -91,6 +91,9 @@
 
 		if(invisibility)				// if invisible, fade icon
 			alpha = 128
+		else
+			alpha = 255
+			//otherwise burying half-finished pipes under floors causes them to half-fade
 
 	// hide called by levelupdate if turf intact status changes
 	// change visibility status and force update of icon
@@ -318,3 +321,9 @@
 			else
 				user << "You need to attach it to the plating first!"
 				return
+
+/obj/structure/disposalconstruct/hides_under_flooring()
+	if(anchored)
+		return 1
+	else
+		return 0

code/modules/recycling/disposal.dm

@@ -940,6 +940,9 @@
 			expel(H, T, 0)
 	..()
 
+/obj/structure/disposalpipe/hides_under_flooring()
+	return 1
+
 // *** TEST verb
 //client/verb/dispstop()
 //	for(var/obj/structure/disposalholder/H in world)