get_chat_msgs() function is split into new get_chat_msgs() without flags
and get_chat_msgs_ex() which accepts booleans instead of bitflags.
FFI call dc_get_chat_msgs() is still using bitflags for compatibility.
JSON-RPC calls get_message_ids() and get_message_list_items()
accept booleans instead of bitflags now.
All contexts created by the same account manager
share stock string translations. Setting translation on
a single context automatically sets translations for all other
accounts, so it is enough to set translations on the active account.
This allows account manager to construct a single event channel and
inject it into all created contexts instead of aggregating events from
separate event emitters.
