Pad hex-encoded string to correct length for ECB and CBC encryption.
public static string Pad( string inputHex, CipherAlgorithm cipherAlg, Padding pad = Padding.Pkcs5 )
Public Shared Function Pad ( inputHex As String, cipherAlg As CipherAlgorithm, Optional pad As Padding = Padding.Pkcs5 ) As String
VB6/C equivalent: PAD_HexBlock