[C] Pass EntityHuman entity for StructureGrowEvent.  Fixes BUKKIT-4493

**The Issue:**
In the update to 1.6.1 the extra parameter passing the entityhuman for the StructureGrowEvent was removed resulting in it always being null within the event.    Commit:  https://github.com/Bukkit/CraftBukkit/commit/a359c7faeaf4d1a0dae72e524788040df1b7025c#L136L32

**PR Breakdown:**
This PR readds the parameter fixing the StructureGrowEvent to once again have the correct player as the cause(When applicable)


**JIRA Ticket:**
https://bukkit.atlassian.net/browse/BUKKIT-4493