Previously, llChar formed an UTF-8-1993 string with the given code and converted that, resulting in multiple question marks when the conversion to Unicode forced by Mono caused errors in multiple characters. They have changed the implementation and now it also considers U+FFFF invalid, and only returns one U+FFFD character if the input is invalid, and LSO behaves the same as Mono (no UTF-8-1993 anymore).
We've also detected problems with Windows (who else would it be) for the Unicode "astral" planes (planes beyond the Basic Multilingual Plane), so now there are new tests that include characters > U+FFFF. And since some builds of Python 2 use UTF-16 internally, we also check llSubString and friends with positions after an astral plane character. This is currently failing under Windows, as there are numerous encoding and line ending problems happening on that OS, especially with Python 3.
