Merge pull request #3402 from fjl/ethclient-api-fixes

core/blockchain.go

core/events.go

core/vm/log.go

core/vm/log_test.go

eth/filters/api.go

eth/filters/filter.go

eth/filters/filter_system.go

eth/filters/filter_system_test.go

ethclient/ethclient.go

ethclient/ethclient_test.go

interfaces.go

mobile/ethclient.go