Fixes the bug resulting from zcash#1904.

…checkpoints, r=str4d

Skip JoinSplit verification before the last checkpoint

Part of #1749

Additional well-formedness check for G2 elements

libsnark currently checks that G<sub>1</sub> and G<sub>2</sub> elements are well-formed by ensuring that they satisfy their respective curve equations, and although this is enough for G<sub>1</sub> (which is instantiated as an order r curve E/F<sub>p</sub>: y^2 = x^3 + b), G<sub>2</sub> is the order r *subgroup* of the composite order r(2q-r) curve E'/Fp<sup>2</sup>: y^2 = x^3 + b/e constructed via a sextic twisting isomorphism. This means we need to ensure these points are order r as well.

None of the proofs on the Zcash blockchain violate this check, and it may not even be possible for them to violate this check (bilinearity is not preserved). Let's be cautious and do it anyway.

Closes zcash#1940

Only increment new notes on reindex

Addresses another issue in zcash#1904.

When an existing one of our notes was found again, its cache was reset and it was re-witnessed. This would cause encountered notes to get out-of-sync with the otherwise-ignored newer notes, which could be a problem if the wallet data happens to be written out during a reindex.

…ebfull

Add total number of commitments to getblockchaininfo

Closes zcash#1943.

exceptions as reference-to-const.

Closes zcash#1941.

…ilable

Closes #1786.

after a successful sign and send, meaning that the logged hash fragment
would be different from the txid logged by "AddToWallet".  This issue
occured when sending from transparent addresses, as utxo inputs must be
signed.  It did not occur when sending from shielded addresses.

Dev

# Conflicts:
#	.gitignore
#	README.md
#	src/Makefile.gtest.include
#	src/gtest/test_checkblock.cpp
#	src/init.cpp
#	src/main.cpp
#	src/main.h
#	src/rpcserver.cpp
#	src/test/checkblock_tests.cpp
#	src/util.cpp

Dev

Dev