A graphical tab bar has two special buttons: on the left side to create
a new tab, and on the right side to close the current tab.  Between them
there is a row of tabs that represent different window configurations.
The name of the tab is the name of the current buffer (just as the name
of the current frame is the name of the current buffer), but a full list
of names of all buffers in a window configuration is displayed in
a pop-up window over the tab.  Clicking the left mouse button switches
between displayed tabs.  The current tab is disabled since there is no
sense to clink it, and also this provides the visual feedback for the
currently selected tab.

There is also a menu "Tabs" that duplicates the tab bar and can be used
on non-graphical terminals.  It binds `C-z t' to the command that
creates a new tab, and `C-z c' to the command that closes the current tab.
`C-z' with a number selects the corresponding tab.  The original command
`suspend-frame' is rebound to `C-z C-z'.