* Enable EIP-2384 for ice age hard fork (#11281)
* ethcore/res: activate agharta on classic 9573000 (#11331)
* Istanbul HF in xDai (2019-12-12) (#11299)
* Istanbul HF in POA Core (2019-12-19) (#11298)
* Istanbul HF in POA Sokol (2019-12-05) (#11282)
* Activate ecip-1061 on kotti and mordor (#11338)
* Enable basic verification of local transactions (#11332)
* Disallow EIP-86 style null signatures for transactions outside tests (#11335)
* Update `add_license` script
* run script
* add `remove duplicate lines script` and run it
* Revert changes `English spaces`
* strip whitespaces
* Revert `GPL` in files with `apache/mit license`
* don't append `gpl license` in files with other lic
* Don't append `gpl header` in files with other lic.
* re-ran script
* include c and cpp files too
* remove duplicate header
* rebase nit
* Add validate_non_zero function
It's used to validate that a Spec's uint field used as a divisor is not zero.
* Add deserialize_with to gas_limit_bound_divisor
Prevents panics due to divide-by-zero on the gas_limit_bound_divisor
field.
* Add deserialize_with to difficulty_bound_divisor
Prevents panics due to divide-by-zero on the difficulty_bound_divisor
field.
* Add validate_optional_non_zero function
Used to validate Option<Uint> divisor fields.
* Use deserialize_with on optional divisor fields.
* Add #[serde(default)] attribute to divisor fields
When using `#[serde(deserialize_with)]`, `#[serde(default)]` must be specified so that missing
fields can be deserialized with the deserializer for `None`.
