Fix MCEternal

[HaHaWTH]

This pull request closes #904.

Changes made

• Move tilesThisCycle to member variable to keep LVT clean and make Mixin happy
• Make iterator can be captured by Mixin

Error analysis

Error log:

[main/ERROR] [mixin]: Critical injection failure: LVT in net/minecraft/world/World::func_72939_s()V has incompatible changes at opcode 787 in callback net/minecraft/world/World::beforeTick.
Expected: [Ljava/util/Iterator;, Lnet/minecraft/tileentity/TileEntity;, Lnet/minecraft/util/math/BlockPos;]
Found: [I, Lnet/minecraft/tileentity/TileEntity;, Lnet/minecraft/util/math/BlockPos;]

The original code Iterator<TileEntity> iterator = null; will be considered as unused by javac and will be optimized to bytecode like this:

0: aconst_null
1: astore_1

Not real code, just for example.

Which causes Iterator is missing in LVT, mod mixins cannot capture the variable and lead to errors. After fixing this, the LVT order should be [Ljava/util/Iterator;, I, Lnet/minecraft/tileentity/TileEntity;]

Also int tilesThisCycle = 0; statement causes inconsistent order in local variable table, made mixins capture the wrong value. Moving to member var resolves this.