rpcserver: Correct verifymessage hash generation. (#192)
rpcserver: Correct verifymessage hash generation. (#192)

* txscript:  Add ScriptVerifyLowS to the standard flags

We've already been generating lowS sigs for quite a while.  This removes
the malleability vector.

This mimics Bitcoin Core commit 49dd5c629df0a08cf3b1ea8085c03312d1a81696

* txscript: Implement CheckLockTimeVerify (BIP0065)

See https://github.com/bitcoin/bips/blob/master/bip-0065.mediawiki for
more information.

This commit mimics Bitcoin Core commit bc60b2b4b401f0adff5b8b9678903ff8feb5867b
and includes additional tests from Bitcoin Core commit
cb54d17355864fa08826d6511a0d7692b21ef2c9

* wire: Export var length string serialization funcs.

This commit exports the ReadVarString and WriteVarString functions so
they are available for callers to use.

A variable length string is encoded as a variable length integer
containing the length of the string followed by the bytes that represent
the string itself.

* rpcserver: Copy btcwallet fix for verifymessage.

jrick/dcrd,jrick/dcrd,decred/dcrd,jrick/btcd,jcmincke/dcrd,decred/dcrd,jcmincke/dcrd,jrick/btcd,jcmincke/dcrd,jrick/btcd