After gathering the sample implementations of SRFIs that are
dependencies for 167 & 168, all of the following tests pass:

chibi-scheme -A . -m '(srfi 167 memory test)' -e '(run-tests)'
chibi-scheme -A . -m '(srfi 167 pack test)' -e '(run-tests)'
chibi-scheme -A . -m '(srfi 168 test)' -e '(run-tests)'