RE: Tab bar

[Drew Adams]

> It would be good to have a tab bar of perspectives, too.

Especially if you are talking about having multiple tab bars of different types,
using something narrow, such as a header line, is better than using huge tabs,
such as were shown.

I don't care one way or the other about tabbar.el itself (I like it, but I'm not
suggesting that is the only way to go), but I think its design of using a header
line is a good one.

With such an approach, we can easily have more than one header line, with, for
example, different backgrounds or whatever, to distinguish the different tab
types (buffers, perspectives, ...).

On the other hand, tabbar.el has a different way of dealing with different types
of tab bar: They are all present in the same header line, but only one is shown
at a time. The first thing in the header line is a button that cycles among the
tab-bar types ("tab sets"). That is very handy, and reduces space.

But it can also be helpful sometimes to see more than one tab set at the same
time (e.g. two header lines, of different tab type), so having that as an option
would be good.