DHCPv6 leases status: Display manufacturer info

[vnxme]

Issues in status_dhcpv6_leases.php for which this PR suggests a solution:

• No manufacturer information is displayed though $mac_man is defined;
• MAC addresses are only imported from NDP which is not always full enough (e.g. when DHCPv6+SLAAC option is used, a machine may have two or more IPv6 addresses assigned, then NDP database will have only the one this client machine prefers, unless you ping the others).

Other:
This PR is a part of changes proposed by #4514.

[vnxme]

For discussion: what if we put MAC and manufacturer information into a separate column like it is done on DHCPv4 leases status page?

[fichtner]

Can you revisit your code on top of the latest code? The page was refactored. I also removed the unused MAC database setup but that doesn't mean it can't be added back :) For details see #4642

[vnxme]

@fichtner No problem, but I'm not sure how to work on the code when the changes you have already merged are not released yet. Although I know it's generally discouraged, I use a real device to make and test some changes and I prefer it being equipped with a stable version.

[fichtner]

I'll let you know when these are shipped. Most likely it will indeed be 21.1.5.

[fichtner]

@vnxme did you take a look at this in 21.1.4 yet? :)

[fichtner]

Sorry I meant 21.1.5 of course.

[vnxme]

@fichtner As agreed, I revisited the code and implemented a more creative idea: underline the MAC part of each applicable DUID, add vendor data (if any) below, add an NDP MAC and the corresponding vendor data (if any) further below (when using CARP, DUID MACs are not equal to NDP MACs), remove MAC/vendor data from the hostname column. Now the DUID column may look like that:

[vnxme]

@fichtner I understand you're busy enough with other important things, but may be you could also take a look at #4524 and #4525 which deal with sorting of DHCPv4/6 leases. Thank you in advance.

[fichtner]

Merged #4524 and #4525 as requested. These will be released in 21.1.7 most likely.

[vnxme]

@fichtner Great, thank you! Resolved a conflict for this PR to be mergeable.

[fichtner]

merged, thanks!

[fichtner]

@vnxme nice work, this is great :)