still better way to urlencode
build 'lines' out of 'slices'
.

clearer accum calls
replace afn with loop

Still undecided on afn in 'tokens', since it's deeply non-tail.
use ssyntax consistently throughout strings.arc

Also added a bunch of tests, many from ken shirriff's docs.
add rainbow tests to old-tests.arc
.
purge findsubseq; just use posmatch
indent
.
pluralize takes an optional plural form

Old idea thanks to zck: http://arclanguage.org/item?id=17992
stop supporting lists in pluralize

Never used; instead news.arc explicitly uses len in one place.
Also, interacts poorly with the 'plural' wrapper.