mm-read-coding-system
mm-read-coding-system is an alias for `read-coding-system' in `mm-util.el
'.
(mm-read-coding-system PROMPT &optional DEFAULT-CODING-SYSTEM)
Read a coding system from the minibuffer, prompting with string PROMPT.
If the user enters null input, return second argument DEFAULT-CODING-SYSTEM.
Ignores case when completing coding systems (all Emacs coding systems
are lower-case).