lldpd: bump to 1.0.20

lldpd: bump to 1.0.20

Also implemented the med fast-start -> lldp fast-start change.
lldpd includes a backwards compat handler for the older med command,
but it's better to make these changes so they align with documentation.

Changes:
https://github.com/lldpd/lldpd/releases/tag/1.0.20

Changes:
    Enable fast start unconditionally (and move its configuration in "configure lldp")
    Make VLAN advertisements configurable
Fix:
    Do not break zero-copy traffic on Linux
    Fix crash on rapid addition/removal of interfaces
    Fix management address selection when pattern is a negative IP address

Signed-off-by: Paul Donald <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/20438
Signed-off-by: Robert Marko <[email protected]>