* lisp/bindings.el (mode-line-collapse-minor-modes): New user
option.
(mode-line-minor-modes): New variable to hold mode line
constructs for minor modes.
(mode-line--make-lighter-menu): New helper function to generate
the menu for hidden minor modes.
(mode-line--minor-modes): New helper function to computer mode
line constructs for minor mode lighters.
(mode-line-modes): Use the new variable 'mode-line-minor-modes',
and adjust the order of elements so the indicator for hidden
minor modes is shown towards the end.
* doc/lispref/modes.texi (Mode Line Basics): Move the paragraph
for 'mode-line-compact' from here...
* doc/emacs/display.texi (Optional Mode Line): ...to here, and
document the new user option.
* etc/NEWS: Annouce the new user option.