enable_quotas setting

[Volker]

Hi rc team!

While looking at PR kern/114766 (now closed) I got the impression the
entry of enable_quotas= is quite confusing users. Also the author of
http://www.freebsddiary.org/quotas.php got that wrong.

It's historically there since 1999 but it's the only ^enable_ entry and
all other enable vars are ^.*_enable.

I'm wondering if that should get corrected and support both forms can be
made (at least for a transitioning time)?

Thanks!

Volker