Log Message:
Changes 2.6.2:
* slot: Handle auto-disconnection when a slot contains a slot
* slot and signal: Correct move constructors and move assignments.
* trackable, slot_base, signal_base, connection: Add some noexcept specs
* trackable, slot, signal: Remove noexcept from move operations.
* slot and signal: Add missing move constructors and move assignments
* signal_impl: =delete copy and move operations.
* typed_slot_rep: =delete unimplemented copy and move operations.
* slot_rep: =delete copy and move operations.