Trailing bytes that must be readable past the end of the lower bit sequence, required by loadUnaligned<uint64_t> reads in the lower accessor.
Declared in <folly/compression/elias_fano/EliasFanoCoding.h>
<folly/compression/elias_fano/EliasFanoCoding.h>
constexpr size_t kLowerTrailingBytes = 8;