constructor functions are ugly, because code is running before
main() starts. Instead, as the registration code for NMSetting types
is insid the GType constructor, we just need to ensure at the
right place, that the GType was created.
The right place here is _register_settings_ensure_inited(), because
that is called before we need the registration information.
We also do this for libnm and libnm-core, where it causes visible changes
in behavior. But if somebody would rely on the hashing implementation
for hash tables, it would be seriously flawed.
nm_setting_user_set_data() rejects invalid keys and values, and
can fail. This API is correct never to fail, like the get_data()
only returns valid user-data.
However, the g_object_set() API allows to set the hash directly but
it cannot report errors for invalid values. This API is used to
initialize the value from D-Bus or keyfile, hence it is wrong
to emit g_critial() assertions for untrusted data.
It would also be wrong to silently drop all invalid date, because
then the user cannot get an error message to understand what happend.
The correct but cumbersome solution is to remember the invalid values
separately, so that verify() can report the setting as invalid.
(cherry picked from commit 1dbbf6fb03)
