…, r=str4d

Closes zcash#2954 and zcash#2959.  Fixes Overwinter issues in sighash_tests.

Implement z_mergetoaddress for combining UTXOs and notes

Closes zcash#2493.

Implements ZIP 201.

…e, r=str4d

Overwinter peer management

Implements ZIP 201.

Part of zcash#2904.

Transaction expiry height

Implements ZIP 203.

- Only applies after Overwinter blockheight.

Closes #754.

Release v1.0.15-rc1

The Equihash check caused block index loading to take around 38x longer.
However, we don't need to check it directly, as the only paths to writing a
block header to disk already go through a proof-of-work check (e.g. receiving a
block over the network). By forcing the block header inside the CBlockIndex to
be re-serialized, we retain the benefits of the consistency check without the
overhead at startup.

Co-authored-by: Brad Miller <brad@z.cash>

Use block hash comparison for consistency check when loading block index

The Equihash check caused block index loading to take around 38x longer.
However, we don't need to check it directly, as the only paths to writing a
block header to disk already go through a proof-of-work check (e.g. receiving a
block over the network). By forcing the block header inside the CBlockIndex to
be re-serialized, we retain the benefits of the consistency check without the
overhead at startup.

Closes zcash#2957.

Overwinter release notes and testnet activation height

Closes zcash#2957.

Release v1.0.15

…it are ghosts

add pindex pubkey33 cache

a few fixes to build scripts

Jl777