BUILD: connection: fix build on clang after the VAR_ARRAY cleanup

BUILD: connection: fix build on clang after the VAR_ARRAY cleanup

Commit 4987a4744 ("CLEANUP: tree-wide: use VAR_ARRAY instead of [0] in
various definitions") broke the build on clang due to the tlv field used
to receive/send the proxy protocol. The problem is that struct tlv is
included at the beginning of struct tlv_ssl, which doesn't make much
sense. In fact the value[] array isn't really a var array but just an
end of struct marker, and must really be an array of size zero.