* core/vm, crypto/bn256: switch over to cloudflare library
* crypto/bn256: unmarshal constraint + start pure go impl
* crypto/bn256: combo cloudflare and google lib
* travis: drop 386 test job
Generator in the current lib uses -2 as the y point when doing
ScalarBaseMult, this makes it so that points/signatures generated
from libs like py_ecc don't match/validate as pretty much all
other libs (including libsnark) have (1, 2) as the standard
generator.
This does not affect consensus as the generator is never used in
the VM, points are always explicitly defined and there is not
ScalarBaseMult op - it only makes it so that doing "import
github.com/ethereum/go-ethereum/crypto/bn256" doesn't generate
bad points in userland tools.
This commit is a preparation for the upcoming metropolis hardfork. It
prepares the state, core and vm packages such that integration with
metropolis becomes less of a hassle.
* Difficulty calculation requires header instead of individual
parameters
* statedb.StartRecord renamed to statedb.Prepare and added Finalise
method required by metropolis, which removes unwanted accounts from
the state (i.e. selfdestruct)
* State keeps record of destructed objects (in addition to dirty
objects)
* core/vm pre-compiles may now return errors
* core/vm pre-compiles gas check now take the full byte slice as argument
instead of just the size
* core/vm now keeps several hard-fork instruction tables instead of a
single instruction table and removes the need for hard-fork checks in
the instructions
* core/vm contains a empty restruction function which is added in
preparation of metropolis write-only mode operations
* Adds the bn256 curve
* Adds and sets the metropolis chain config block parameters (2^64-1)
