Optimisations

[stevehalliwell]

• Multi var is used a lot and does a lot of bytecode and stack gymnastics, can probably be better.
• often see chains of get local, we could do a get locals so we can get up to 3 locals in 1 op
• often see chains of push value int with numbers that fit in bytes, push value bytes, with 2 bytes in it
• packet size isn't actually 4 bytes like we want it to be