The calculation used to be wrong when exactly at a power of 2.
`nearest_shift` always return the "next" power of 2
`nearest_shift(4) == 3 # 2^3 = 8`.
On the other hand `next_power_of_2` returns the exact value if that
value is a power of 2 (i.e. `next_power_of_2(4) == 4`).
I.e. :
```
WARN_PRINT(itos(next_power_of_2(4)) + " " + itos(1 << nearest_shift(4)));
// WARNING: ... : 4 8
```
Is this by design?