g_type_init() has been deprecated (and also marked with the attribute
'deprecated') since glib 2.36 as the type system is automatically
initialized. Since the minimum version of glib required by ModemManager
is 2.36, calling g_type_init() isn't necessarily in the ModemManager
code.
Split out the %IPDPADDR parsing into a helper and add testcases for it,
and add support for IPv6 handling. If the returned IPv6 is link-local,
the address should be assigned to the interface and SLAAC performed to
retrieve the actual IPv6 prefix and RDNSS/DNSSD information.