getSourceSet and getTargetSet are incorrectly implemented. Whenever a string is
affected, but not all of its constitutant characters are, only the string should
be added, not the constituants. While this cannot be exact, it should be much
closer than it is now.
The way to do this for RB transliterators is: (e.g. with getSource) as you are
walking through the rules, store as follows:
To the result add each of "ab", "c". Don't add $v1, since it is preserved in the
output. Case 2 might be too hard initially; if so, do later.