sort-coding-systems-predicate is a variable defined in `mule-cmds.el'.
Its value is
nil
This variable may be risky if used as a file-local variable.
Documentation:
If non-nil, a predicate function to sort coding systems.
It is called with two coding systems, and should return t if the first
one is "less" than the second.
The function `sort-coding-systems' use it.