System endianness bug affecting nanonext 0.9.2

[shikokuchuo]

nanonext 0.9.2 brought performance enhancements to serialisation / unserialisation by moving this to a lower level.

Part of the gains was to allow use of system endianness for serialisation, which is fine as unserialisation can automatically account for this. So this is not an issue even for sending/receiving between systems with different endianness.

However the same underlying functions were adopted by the sha / base64 functions, which is now problematic as the output will differ depending on system endianness.

[shikokuchuo]

The above commit will fix this issue for all releases > 0.9.2, by always using big endian.