Change gas & related fields to unsigned integer type (#2839)

* Change gas & related fields to unsigned integer type
* Implement AddUint64Overflow

server/init.go

@@ -15,7 +15,6 @@ import (
 	tmtypes "github.com/tendermint/tendermint/types"
 )
 
-
 // SimpleGenTx is a simple genesis tx
 type SimpleGenTx struct {
 	Addr sdk.AccAddress `json:"addr"`
@@ -23,7 +22,6 @@ type SimpleGenTx struct {
 
 //_____________________________________________________________________
 
-
 // Generate a genesis transaction
 func SimpleAppGenTx(cdc *codec.Codec, pk crypto.PubKey) (
 	appGenTx, cliPrint json.RawMessage, validator types.GenesisValidator, err error) {