Sort coding system list CODINGS by a priority of each coding system.
Return the sorted list. CODINGS is modified by side effects.
If a coding system is most preferred, it has the highest priority.
Otherwise, coding systems that correspond to MIME charsets have
higher priorities. Among them, a coding system included in the
`coding-system' key of the current language environment has higher
priority. See also the documentation of `language-info-alist'.
If the variable `sort-coding-systems-predicate' (which see) is
non-nil, it is used to sort CODINGS instead.