I forgot to update one instance of "go-ethereum" in commit 3f047be5.

All code outside of cmd/ is licensed as LGPL. The headers
now reflect this by calling the whole work "the go-ethereum library".

TestMadeupParentBlockChainAttack has been deleted because it was too
hard to port and the attack that it checks the prevention of is being
averted in a different way (through a protocol change).