Use != 0 instead of > 0 for unsigned integer types

[code423n4]

Handle

pmerkleplant

Vulnerability details

When dealing with unsigned integer types, comparisons with != 0 are cheaper
then with >0.

Therefore, the following statements can be refactored to save gas:

./Locke.sol:226: if (acctTimeDelta > 0 && ts.tokens > 0)
./Locke.sol:236: if (tdelta > 0 && unstreamed > 0)
./Locke.sol:378: require(amount > 0, "amt");
./Locke.sol:418: require(amount > 0, "amt");
./Locke.sol:456: require(amount > 0, "amt");
./Locke.sol:522: require(amount > 0, "amt");
./Locke.sol:536: require(amount > 0, "amt");
./Locke.sol:572: require(rewardAmt > 0, "amt");
./Locke.sol:612: if (fees > 0)
./Locke.sol:679: if (incentives[token] > 0)

[0xean]

dupe of #143