message: doc: clarify CRollingBloomFilter size estimate
diff: @@ -94,7 +94,18 @@ public:
  * insert()'ed ... but may also return true for items that were not inserted.
  *
  * It needs around 1.8 bytes per element per factor 0.1 of false positive rate.
  - * (More accurately: 3/(log(256)*log(2)) * log(1/fpRate) * nElements bytes)
  + * For example, if we want 1000 elements, we'd need:
  + * - ~1800 bytes for a false positive rate of 0.1
  + * - ~3600 bytes for a false positive rate of 0.01
  + * - ~5400 bytes for a false positive rate of 0.001
  + *
  + * If we make these simplifying assumptions:
  + * - logFpRate / log(0.5) doesn't get rounded or clamped in the nHashFuncs calculation
  + * - nElements is even, so that nEntriesPerGeneration == nElements / 2
  + *
  + * Then we get a more accurate estimate for filter bytes:
  + *
  + * 3/(log(256)*log(2)) * log(1/fpRate) * nElements
  */
  class CRollingBloomFilter
  {
  