Use setq rather than nested let*.
Parse hexadecimal number format upper case.
Simplify call to supplied mapper function.
Make 'cl compile-time dependency.
Re-use the slot reserved for the end-of-word marker to store a caller
supplied sort key for that word.
Provide access to the number of keys stored in the dictionary.
Lexical-let-bind the variable for the mapper function as this
identifier is used in `folio-map-mafsa' too, only with a different
number of arguments.