Follows cl-icu 06d1f63: cl-ffi loads libicuuc again when a saved image
starts and runs load-icu as one of its image-start hooks, so cl-icu/sys
is gone; the examples use cl-ffi's operators, loading libicui18n from a
file name as cl-ffi's load-foreign-library takes one, and a Homebrew ICU
is found through DYLD_FALLBACK_LIBRARY_PATH.