Type LuaJIT code as much as possible

[Rerumu]

Right now LuaJIT code suffers a performance penalty because the JIT is not always capable of inferring that operations on i32 are for integers. This causes a lot of f64-oriented native code to be generated that could have been i32 operations.

I don't know of any good ways of passing in strong type hints to the JIT other than just replacing all uses of i32 with the i64 type and truncating results.