perl5: change default perl from 5.16 to 5.22

[dbevans (David B. Evans)]

As ​mf2k has recently mentioned, as we come to the end of the year, its probably a good time to change the default perl from perl5.16 to perl5.22.

Tasks to accomplish:

• change the default variant of port perl5 to +perl5_22
• change the hardcoded fallback perl branch in the perl5 port group from 5.16 to 5.22
• update any ports that declare perl variants to use the perl5 port group without forcibly declaring the default variant. This will allow these ports' default variant to automatically follow that defined by the perl5 port group, simplifying future updates. At this point, I believe there are only two ports that need attention.

I realize that there are currently many ports left that depend explicitly on perl versions other than perl5.22 (#48365) but I don't see that as a gating task for executing this ticket. Of course, they will have to be updated before any further outdated perls can be removed and perhaps changing the default will provide an incentive to finish these updates.

Let me know if you have any comments or suggestions reguarding this proposal. Otherwise, I will go ahead and make the changes in the next few days. I've already made the changes in my local port repo and they appear to work well.

Ports that currently set the default perl variant forcibly (other than perl5) and don't use the perl5 port group:

• biblatex-biber (dports, openmaintainer)
• percona-toolkit (pixilla, openmaintainer)

[mojca (Mojca Miklavec)]

"unified" Perl port (preliminary)