removed obsolete boost workaround (boost ticket #4258)

removed obsolete boost workaround (boost ticket bitcoin#4258)

1.3.0.0: Merge dev to release

…e's inputs to the wallet

3a7ec7c [Tests] Add wallet_reorg-stake functional test to test_runner.py (random-zebra)
a0285e4 [Wallet] Fix bug with coinstake inputs wrongly marked as spent (random-zebra)
bb683c7 [Tests] Add wallet_reorg-stake functional test (random-zebra)
3eca8da [Core][Tests] REGTEST: fix nStakeModifier=0 (random-zebra)

Pull request description:

  Additional bug introduced with the changes of bitcoin#970 (and not caught in bitcoin#1040 even though the culprit is the same: `GetDepthInMainChain` returning a value `0` when `-1` was expected).

  After a block reorganization, the coins used as coinstake inputs in the orphan chain were still marked as spent in the wallet. Thus there were inconsistencies in the balance (either displayed in the GUI or returned by `getbalance` via CLI) and missing utxos in the wallet (either accessed through coincontrol in the GUI or returned by `listunspent` via CLI).

  PIVX-Project@a0285e4 fixes it by marking as "spent" the inputs of not-in-mempool txes only for non-coinstakes (coinstakes don't hit the mempool so, when not in chain, their inputs should be considered unspent).

  PIVX-Project@bb683c7 Introduces the functional test `wallet_reorg-stake` to reproduce the issue.
  The test fails without PIVX-Project@a0285e4 and passes with it.

ACKs for top commit:
  Warrows:
    ACK 3a7ec7c

Tree-SHA512: 8f97e3d48720b776c84820e0ab8257665ac4c4c9d394db0e4b9f3a05b0904bf9f70cf54865338c4e29066e6b3670e9e90f77780d3ddd198e8e2b6e416c4cb49c