Checks to see if the Ldap v3 protocol is used. Normally this would
extract a version number from the bind request sent by the client
indicating the version of the protocol to be used in this protocol
session. The integer is either a 2 or a 3 at the moment. We thought it
was better to just check if the protocol used is 3 or not rather than use
an type-safe enumeration type for a binary value. If an LDAPv4 comes out
then we shall convert the return type to a type safe enumeration.