Gas Optimizations

[code423n4]

1. Reorder Struct for saving more gas

https://github.com/fei-protocol/flywheel-v2/blob/77bfadf388db25cf5917d39cd9c0ad920f404aad/src/token/ERC20Gauges.sol#L52

This implementation below can saving more gas instead

##Recommendation Mitigation

    struct Weight {
        uint32 currentCycle;
        uint112 storedWeight;
        uint112 currentWeight;
    }

2. change uint256 i = 0 into uint i for saving more gas

using this implementation can saving more gas for each loops.

##Tool Used
Manual Review

##Recommended Mitigation
Change it

##Occurances

src/token/ERC20MultiVotes.sol#L346
src/token/ERC20Gauges.sol#L134
src/token/ERC20Gauges.sol#L184
src/token/ERC20Gauges.sol#L307
src/token/ERC20Gauges.sol#L384
src/token/ERC20Gauges.sol#L564

3. Saving gas by removing = 0

https://github.com/fei-protocol/flywheel-v2/blob/77bfadf388db25cf5917d39cd9c0ad920f404aad/src/token/ERC20MultiVotes.sol#L354

If a variable was not set/initialized, it is assumed to have default value to 0
this implementation was used for saving more gas by removing = 0

##TOOLS USED
Manual Review

##Mitigation Step
Remove = 0

[thomas-waite]

Much prefer explicitly sized variables over uint even if it does cost a bit more gas. How does that struct difference save gas?