Emacs 24.3 Common Lisp Package Name Change
if you get warning messages like these:
- `flet' is an obsolete macro (as of 24.3); use either `cl-flet' or `cl-letf'.
- `labels' is an obsolete macro (as of 24.3); use `cl-labels' instead.
don't worry about it. Those functions are from Common Lisp library. In emacs 24.3, they made changes to the naming so most of them now starts with “cl-”.
most packages are still using the old name, and may not switch over for a while. Because, if one simply switch, then it won't work with older emacs. They have to check version first, or set up alias, but that gets a bit involved.
see also Emacs 24.1 Features (released 2012-06)
thanks to _roowe_ for asking.