v0.94.4.65
Everything except cancelling the MELTING snowman damage can be added for a 1.2.3 build.
You could, however, have the dev builds beyond .64 be meant for 1.2.4+, as these are mainly
additions, and not bug fixes, per se.

Added/Fixed/Changed
-------------------
Built against 1.2.4 just cause of Iron Golems and Melting damage cancellation
Listed line numbers are the current line numbers, not what they used to be

added 2 new health amounts for boss health: verylow/veryhigh
veryhigh replaced psycho, and psycho is now even more psycho
    (in BossHealth[line 7])

allow players to build Snowmen and Iron Golems in the arena while it's running
Coinciding with this come 1.2.4, cancel Damage Cause of "MELTING" to keep them alive
and not be fireproof. (specifically build # 2102 and beyond)
    (in ArenaListener:
     onCreatureSpawn() and onEntityDamage())

add both snow and iron golems to a set to watch (and clear) during arena matches
inform all arena participants that a golem has died, and remove from set
    (Pumpkin Spout announcement material)
    (in ArenaListener:
     onMonsterDeath() and onCreatureSpawn())

    (in MonsterManager:
     added a HashSet<LivingEntity> golems[lines 22, 30, 39, 49, and 89-99])

    (in Msg:
     new Msg.GOLEM_DIED[line 31]
     added into announcements.properties, as well as the pirate announcements.
     I'm not translating it into the other 5 languages :P)

Implemented a forced "/ma leave" situation where a player wanders out of the spectator
area and proceeds to try and drop an item. Normally, it's denied, and many people scream
"Fix this bug!". Well, it's not a bug, and there should be a message informing them
to use "/ma leave" beforehand next time. Placeholder message used for now
    (in ArenaListener:
     onPlayerDropItem())

fixed the check in the EntityCombustEvent to make Zombies/Skeletons not be fireproof
    (in ArenaListener:
     onEntityCombust())

added ability to have Ocelots and Iron Golems in the waves (ocelot(s) & iron-golem(s))
Iron Golems do a lot of damage (1-1.5 hears in full diamond)
Ocelots seem to not do anything besides run away.
    (in MACreature lines 45-48)

Untested
--------
changed a piece in Obsidian Bomb[line 30]
    ( target.getLocation() -> loc, since loc is already == to target.getLocation() )

Not high priority
although is tested
------------------
Ocelots as pets if Raw Fish is found in the inventory
Ocelots seem to not like to attack, but their Creeper Deterent still works.
    (in MonsterManager:
     HashSet<Wolf> -> HashSet<Tameable>[lines 23 & 30], fix return/param types on
     getPets and addPet, added Ocelots to removePets[lines 101-132],
     and finally, the 2 new imports[lines 12 & 14])

    (in ArenaClass:
     "int pets;" -> "int wolves, cats;"[line 22]
     wolves & cats = 0 to start[lines 34-35]
     check for RAW_FISH in inventory[lines 105-107]
     getPetAmount refactored to getWolfAmount[lines 229-231]
     getCatAmount added[lines 233-239])

    (in ArenaImpl:
     fixed spawnPets() to account for Ocelots now[lines 677-716])

    (in ArenaListener:
     changed Wolf damagee/damager checks to be any Tameable creature
     onMonsterDamage())

    (in MobArenaHandler/ArenaMaster/ArenaMasterImpl:
     changed isPetInArena() and getArenaWithPet() calls to be living entity neutral (wolf -> pet))