16. The method of claim 15 , further comprising: determining that at least one of the one or more existing client font ranges corresponds to a master font range which, in the master font range ordering, is preceded by a master font range corresponding to one of the one or more new client font ranges; and in response to said determining, indicating in the generated instructions that said consecutively enumerating the combined set of client font ranges shifts the at least one of the one or more existing client font ranges to a higher position.
15. The method of claim 13 , wherein the generated instructions include instructions for: establishing one or more new client font ranges, wherein each of the one or more new client font ranges corresponds to one of the plurality of master font ranges containing a glyph of the font subset that is not contained in any of the one or more master font ranges corresponding to the one or more existing client font ranges; consecutively enumerating a combined set of client font ranges comprising the one or more new client font ranges and the one or more existing client font ranges, wherein said consecutively enumerating the combined set of client font ranges preserves the order of precedence established by the master font range ordering; and placing each of the glyphs in the extensible data structure in the client font range whose corresponding master font range contains the glyph.