This function yields the largest power of 2 less than or equal to the given number.

Relative to the Java standard library, which provides this function, there is a gap in the Haskell library, even though the Haskell docs describe a method to calculate logBase2 via the `countLeadingZeros` function.

From the Java documentation:

The implementations of the "bit twiddling" methods (such as highestOneBit and numberOfTrailingZeros) are based on material from Henry S. Warren, Jr.'s ''Hacker's Delight'', (Addison Wesley, 2002).