[sfnt] Fix `OS/2' table version 5 support. We now follow the `official' announcement from Microsoft (on the OpenType mailing list, which unfortunately hasn't a public archive). * include/freetype/tttables.h (TT_OS2): s/usLowerPointSize/usLowerOpticalPointSize/, s/usUpperPointSize/usUpperOpticalPointSize/. * src/sfnt/ttload.c (tt_face_load_os2): Update, and set correct default values.