The code that allowed "..." to be expanded in the "*Backtrace*" buffer
should now work anywhere the data is generated by 'cl-print'.
+*** The 'backtrace-ellipsis' button is replaced by 'cl-print-ellipsis'.
+
*** hash-tables' contents can be expanded via the ellipsis.
+*** Modes can control the expansion via 'cl-print-expand-ellipsis-function'.
+
** Modeline elements can now be right-aligned.
Anything following the symbol 'mode-line-format-right-align' in
'mode-line-format' will be right-aligned. Exactly where it is