The bug is that it's possible to include a participating validator which has custody bit one *without* specifying that validator in `attestation.aggregation_bitfield`. In other words, we want to check that every bit in `custody_bitfield` is zero whenever the corresponding bit in `aggregation_bitfield` is zero. Well spotted @protolambda
Substantive changes:
1) Split the inclusion delay reward between attester and proposer to add up to at most one base reward. This is analogous to the reward logic in `slash_validator`, and makes the `BASE_REWARDS_PER_EPOCH` constant include proposer rewards.
2) Double `BASE_REWARD_FACTOR` to 2^6 (addressing item 4 in #1054). When the total effective balance is 2^17 ETH then maximum annual issuance is a bit below 2^21 ETH. Maximum annual issuance happens when a) all validators make perfect attestations (matching source, target, head, as well as consistent crosslink data), b) all attestations are included as fast as possible (in particular, no skip blocks), and c) there are no slashings.
```python
BASE_REWARD_FACTOR = 2**6
SLOTS_PER_EPOCH = 2**6
SECONDS_PER_SLOT = 6
BASE_REWARDS_PER_EPOCH = 5
GWEI_PER_ETH = 10**9
MAX_TOTAL_EFFECTIVE_BALANCE = 2**27 * GWEI_PER_ETH
TARGET_MAX_ISSUANCE = 2**21 * GWEI_PER_ETH
def integer_squareroot(n: int) -> int:
"""
The largest integer ``x`` such that ``x**2`` is less than or equal to ``n``.
"""
assert n >= 0
x = n
y = (x + 1) // 2
while y < x:
x = y
y = (x + n // x) // 2
return x
MAX_REWARDS_PER_EPOCH = MAX_TOTAL_EFFECTIVE_BALANCE * BASE_REWARD_FACTOR // integer_squareroot(MAX_TOTAL_EFFECTIVE_BALANCE) // BASE_REWARDS_PER_EPOCH
EPOCHS_PER_YEAR = 365.25*24*60*60 / (SECONDS_PER_SLOT * SLOTS_PER_EPOCH)
MAX_REWARDS_PER_YEAR = EPOCHS_PER_YEAR * MAX_REWARDS_PER_EPOCH * BASE_REWARDS_PER_EPOCH
print(MAX_REWARDS_PER_YEAR / TARGET_MAX_ISSUANCE)
```
