Only allow command blocks to be placed by op'd players

nms-patches/PlayerInteractManager.patch

@@ -1,5 +1,5 @@
---- ../work/decompile-8eb82bde//net/minecraft/server/PlayerInteractManager.java	2014-12-09 12:19:57.555618161 +0000
-+++ src/main/java/net/minecraft/server/PlayerInteractManager.java	2014-12-09 12:16:26.307622849 +0000
+--- ../work/decompile-8eb82bde/net/minecraft/server/PlayerInteractManager.java	2014-12-21 19:03:39.124516788 +0000
++++ src/main/java/net/minecraft/server/PlayerInteractManager.java	2014-12-21 19:03:39.128516787 +0000
 @@ -1,5 +1,13 @@
  package net.minecraft.server;
  
@@ -216,7 +216,7 @@
          if (this.gamemode == EnumGamemode.SPECTATOR) {
              TileEntity tileentity = world.getTileEntity(blockposition);
  
-@@ -312,6 +444,68 @@
+@@ -312,6 +444,72 @@
                  return itemstack.placeItem(entityhuman, world, blockposition, enumdirection, f, f1, f2);
              }
          }
@@ -229,7 +229,11 @@
 +            if (this.gamemode == EnumGamemode.SPECTATOR) {
 +                TileEntity tileentity = world.getTileEntity(blockposition);
 +                cancelledBlock = !(tileentity instanceof ITileInventory || tileentity instanceof IInventory);
-+            }           
++            }
++
++            if (!entityhuman.getBukkitEntity().isOp() && itemstack != null && Block.asBlock(itemstack.getItem()) instanceof BlockCommand) {
++                cancelledBlock = true;
++            }
 +            
 +            PlayerInteractEvent event = CraftEventFactory.callPlayerInteractEvent(entityhuman, Action.RIGHT_CLICK_BLOCK, blockposition, enumdirection, itemstack, cancelledBlock);
 +            firedInteract = true;