Let's add a generic parser for VLAN ids, which should become handy as
preparation for PR #3428. Let's also make sure we use uint16_t for the vlan ID
type everywhere, and that validity checks are already applied at the time of
parsing, and not only whne we about to prepare a netdev.
Also, establish a common definition VLANID_INVALID we can use for
non-initialized VLAN id fields.
This patch removes includes that are not used. The removals were found with
include-what-you-use which checks if any of the symbols from a header is
in use.
- Rename log_meta() → log_internal(), to follow naming scheme of most
other log functions that are usually invoked through macros, but never
directly.
- Rename log_info_object() to log_object_info(), simply because the
object should be before any other parameters, to follow OO-style
programming style.
