when the character is not defined and the corresponding '.notdef' glyph isn't included in a truetype font we now default to a zero width character. it might be that we should use the default/missing width instead but this will work ok for most use-cases.
the individual cff parser uses a cff dictionary reader inside it which has a per-instance operands list, for this reason it is not thread-safe and cannot be shared. this change creates a new individual font parser for each call to the top-level cff parser.
where the value is 28 the next two bytes indicate a short, not a 16 bit two's complement number, apparently, or i've misunderstood what the two's complement bit is about...
the byte value of 28 indicates the next 2 bytes are a 16 bit two's complement number rather than just a short. this changes the calculation to generate the two's complement value correctly.
the brute force searcher offsets were off by one. this change means the offset returned is now aligned with the object number in the object number/generation/operator triple.
multiple master fonts are an extension of the adobe type 1 font format. we don't have any special case handling for them so for now we default to attempting to use the adobe type 1 font handler. it may be that we need some special parsing logic but the test file using the mmtype1 fonts didn't actually specify any font bytes so we can't check.
decimal numbers were dependent on the current thread culture for the output file. this meant values like '70.679' were output as '70,679' for cultures using a comma rather than period separator for the floating point (i.e. the whole world). this resulted in the file displaying incorrectly.
