[scudo] Change isPowerOfTwo macro to return false for zero. (#87120)

Clean-up all of the calls and remove the redundant == 0 checks.

There is only one small visible change. For non-Android, the memalign
function will now fail if alignment is zero. Before this would have
passed.

GitOrigin-RevId: ed6edf262d9061ce3c024754c4981299b5184ee2
3 files changed