depends: Gitian 0.10 fixes

Github-Pull: #5465
Rebased-From: 422f873ef3d62f7dff9c00dc0f221912ce28f130 d546191dc28fac0e365c8f2aba47ac69a8920d6c d7db4b6317fd9c79bd6fd7c7455d7186b306411f e27d7cb24835c6ce16c12eb758c2d75806103c4a
signrawtransaction: validate private key.

Github-Pull: #5461
Rebased-From: aa768f1848b00e0fd615016598d3fb1f1da240ed
Merge remote-tracking branch 'bitcoin/0.10' into 0.10
Make CScriptNum() take nMaxNumSize as an argument

While the existing numeric opcodes are all limited to 4-byte bignum
arguments, new opcodes will need different limits.
Move LOCKTIME_THRESHOLD to src/script/script.h

Will now be needed by CHECKLOCKTIMEVERIFY code.
Replace NOP2 with CHECKLOCKTIMEVERIFY

<nLockTime> CHECKLOCKTIMEVERIFY -> <nLockTime>

Fails if tx.nLockTime < nLockTime, allowing the funds in a txout to be
locked until some block height or block time in the future is reached.

Only the logic and unittests are implemented; this commit does not have
any actual soft-fork logic in it.

Credit goes to Gregory Maxwell for the suggestion of comparing the
argument against the transaction nLockTime rather than the current
time/blockheight directly.
Enable block nVersion=3 CHECKLOCKTIMEVERIFY upgrade process
Hack around removed CTransaction from EvalScript etc.

Caused by bitcoin/bitcoin 4890 breaks CHECKLOCKTIMEVERIFY
because there is no longer access to toTx for some strange reason