As we aren't really using the standarized SHA-3

Created alternate versions of Trie and SecureTrie functions that can return a MissingNodeError (used by ODR services)

Fixed database merge strategy to use the correct database. Due to a copy
paste fail when doing type evaluation the same database was being
iterated (chain), all others were ignored.

Removed state prefixing because {H(code): code} is stored in the same
database as the rest of the state.

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".