Fixes:
+• Following Unicode Corrigendum #9, the noncharacters U+nFFFE, U+nFFFF,
+ U+FDD0..U+FDEF are allowed in UTF-8 strings again.
+ (fd.o #63072, Simon McVittie)
+
• Diagnose incorrect use of dbus_connection_get_data() with negative slot
(i.e. before allocating the slot) rather than returning junk
(fd.o #63127, Dan Williams)