MAJOR: spoe: upgrade the SPOP version to 2.0 and remove the support for 1.0

MAJOR: spoe: upgrade the SPOP version to 2.0 and remove the support for 1.0

The commit c4dcaff3 ("BUG/MEDIUM: spoe: Flags are not encoded in network order")
introduced an incompatibility with older agents. So the major version of the
SPOP is increased to make the situation unambiguous. And because before the fix,
the protocol is buggy, the support of the version 1.0 is removed to be sure to
not continue to support buggy agents.

The agents in the contrib folder (spoa_example, modsecurity and mod_defender)
are also updated to announce the SPOP version 2.0.

So, to be clear, from the patch, connections to agents announcing the SPOP
version 1.0 will be rejected.

This patch must be backported in 1.8.