eo_cxx: Fix signal_connection disconnect crash

eo_cxx: Fix signal_connection disconnect crash

Fixed crash when disconnecting event inside of its own event callback.
Instead of deleting the callback object immediately during disconnection
(which causes the callback to be freed), the deletion is now scheduled
for later (using ecore_main_loop_thread_safe_call_async).

Updated some Makefiles to proper include ecore now that it is used in
all event wrappers.

Added a unit test to verify crashes under these circumstances.