Bukkit/CraftBukkit — pull request #607 by wilsonsd (2011-12-23 19:34:52+00:00)
Title: Throw BlockPlaceEvent when changing a single step to a double step. 

BUKKIT-394 fix.

Issue BUKKIT-394: When a player places a step on top of another step
to form a double step, no BlockPlaceEvent is thrown.

Reason for bug: When a player places a step on top of a single step,
ItemStep.a line 38 detects this and prevents the call to ItemBlock.a
on line 46. But ItemBlock.a is where CraftBukkit creates and fires
the BlockPlaceEvent.

Fix: Remove the check in ItemStep.a. Rather than detecting the new
double-step in ItemStep, we'll detect it in ItemBlock.a. This way, we
create a BlockPlaceEvent in the usual way.