fixed assigning negative number to unsigned
fixed assigning negative number to unsigned

debris/solidity,gluk256/solidity,chriseth/solidity-doc-test,LianaHus/solidity,douglas-larocca/solidity,vaporry/solidity,ruchevits/solidity,ruchevits/solidity,chriseth/solidity,arkpar/solidity,ethers/solidity,shahankhatch/solidity,ruchevits/solidity,ruchevits/solidity