Do not call std::make_shared on classes inheriting from
std::enable_shared_from_this when compiling with g++ 8.2.
* NEWS: Mention the bug.
* spot/misc/common.hh (SPOT_make_shared_enabled__): New macro.
* spot/twa/twagraph.cc, spot/twa/twagraph.hh, spot/twa/twaproduct.hh,
spot/twa/taatgba.hh, spot/twaalgos/couvreurnew.cc,
spot/twaalgos/magic.cc, spot/twaalgos/se05.cc, spot/twaalgos/tau03.cc,
spot/twaalgos/tau03opt.cc, spot/twaalgos/gv04.cc,
spot/ltsmin/ltsmin.cc, spot/twaalgos/gtec/gtec.cc: Use it.