Added further diagnostic detail in case of transaction ID clash.
Correct format of AuxPow coinbase script.

AuxPoW coinbase scripts now include block height as per BIP0034, which also
resolves issue of transactions being generated which collide.
Correct AuxPoW coinbase script concatenation operators.

MakeCoinbaseWithAux() was incorrectly using << to add a CScript onto a
CScript instead of the + operator. Operators corrected and structure
now more closely reflects coinbase script assembly done elsewhere.
check block version for aux blocks properly for version warning

UpdateTip() was checking block versions against one of two
possible AuxPoW versions. Added consts for version checks and
IsAuxPowVersion(int nVersion) for use with UpdateTip()'s
block version check.
Disable AuxPoW RPC commands until switchover block

AuxPoW RPC commands now return a failure message until the switchover block on the respective
network. Also cleaned up RPC error values to use enum values rather than magic numbers.
Set AuxPoW switchover block to 371337
Merge pull request #613 from rnicoll/1.8-dev-coinbase

Correct format of AuxPoW coinbase script
Merge pull request #616 from patricklodder/1.8-dev-auxpow-version

check block version for aux blocks properly for version warning
Merge pull request #620 from rnicoll/1.8-dev-rpc

Disable AuxPoW RPC commands until switchover block
Merge pull request #621 from rnicoll/1.8-dev-block

Set AuxPoW switchover block to 371337