======VPOP3.HexString======
Added in VPOP3 8.7

This function returns a Hex string encoding of the supplied parameter

  VPOP3.HexString(text)

or

  VPOP3.HexString(byte-array)
  
It can be passed either a text string or a table containing one byte per table-entry (eg as returned from the [[VPOP3.HMAC]] or [[Lua Hashing Functions]]

It returns a string containing the Hex encoding of the string - 2 characters per byte, in lower case.

If there was an error, it returns a Nil value