Primary and rogue symbols were being set to default if primary hadn't
been given a value, possibly clobbering rogue symbols if those had
been given a value. Initialize them independenly.
Return early from curses_convert_glyph() if the value doesn't have
the 8th bit set since it now deals exclusively with DECgraphics
handling. Force a sane value for returning early on rogue level.
61b976e0d5