[Bleeding] Add all blocks needed to PortalCreateEvent. Fixes BUKKIT-5464

Due to changes in how portals were created in Minecraft 1.7, the code that
was previously used to find the blocks involved in the PortalCreateEvent
no longer detected all blocks. Additionally, in the process of updating to
1.7.2, a missed diff resulted in some blocks that were found not being
properly added to the blocklist. This commit corrects that missed diff,
while also adding a check to ensure that the top and bottom of the portal
frame are included in the blocklist.