The version of the CredSSP protocol can be 2 or 3

According to Microsoft documentation, valid values for the Version field are 2 and 3. Newer servers (like Windows 2012 R2) respond with Version=3.

Change-Id: Ifb0c6f52d09c75bbde2b4a46d13366461736b9c0
Reviewed-on: https://code.wireshark.org/review/3527
Reviewed-by: Pascal Quantin <pascal.quantin@gmail.com>