======VPOP3.UnHexString======
Added in VPOP3 8.7

This function Decodes a Hex string into the original data

  VPOP3.UnHexString(hex-text)

The input hex-text should have no extra spaces or punctuation, and be two hex digits per result byte. Any pairs of characters which are not valid hex will be processed as a 'zero' byte.

It returns a table containing the decoded data bytes - one byte per table entry.

If there was an error, it returns a Nil value