previousClearBit
Returns the biggest index of a bit which value is false
before startIndex (inclusive). Returns -1 if there is no such bits before startIndex or if startIndex == -1. If startIndex>= size will return startIndex assuming that the set has an infinite sequence of false
bits after (size - 1)-th.
Since Kotlin
1.3Throws
IndexOutOfBoundException
if startIndex< -1.