constant strings to s-ops (the wrap function)

[gailweiss]

when converting a constant to an s-op, handle conversion of strings with multiple characters as well, e.g. so "aa" is actually interpreted as ["aa",...,"aa"] repeated as many times as the input length. things like tokens=="aa" act weird without this. this does not affect handling of string inputs in general, e.g. length("hi") is still [2.0,2.0]