[pull] master from ethereum:master (#27)

* internal/ethapi: default to zero address for calls (ethereum#20702)

This makes eth_call and eth_estimateGas use the zero address
as sender when the "from" parameter is not supplied.

Co-authored-by: Felix Lange <[email protected]>

* les: separate peer into clientPeer and serverPeer (ethereum#19991)

* les: separate peer into clientPeer and serverPeer

* les: address comments

* mobile: add CallOpts.SetFrom (ethereum#20721)

This was missing because I forgot to wrap it when bind.CallOpts.From
as added.

* crypto/bn256: fix import line (ethereum#20723)

* p2p/discv5: fix test on go 1.14 (ethereum#20724)

Co-authored-by: Martin Holst Swende <[email protected]>
Co-authored-by: Felix Lange <[email protected]>
Co-authored-by: gary rong <[email protected]>
Co-authored-by: Adam Schmideg <[email protected]>