Library::CallNumber::LC is mostly designed to do call number
normalization, with the following goals:
* The normalized call numbers are comparable with each other, for
  proper sorting
* The normalized call number is a short as possible, so left-anchored
  wildcard searches are possible (e.g., searching on "A11*" should
  give you all the A11 call numbers)
* A range defined by start_of_range and end_of_range should be
  correct, assuming that the string given for the end of the range
  is, in fact, a left prefix.