optimize PutLeNN functions by using bswap
optimize PutLeNN functions by using bswap

BenchmarkWrites/le16-4           1040          678           -34.81%
BenchmarkWrites/le32-4           1168          861           -26.28%
BenchmarkWrites/le64-4           2073          1628          -21.47%

bamiaux/iobit,bamiaux/iobit