couple of curses symbol handling bits

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.

win/curses/cursinit.c

@@ -785,10 +785,11 @@ curses_init_options()
     set_option_mod_status("eight_bit_tty", SET_IN_FILE);
 
     /* If we don't have a symset defined, load the curses symset by default */
-    if (symset[PRIMARY].fallback) {
+    if (symset[PRIMARY].fallback)
         load_symset("curses", PRIMARY);
+    if (symset[ROGUESET].fallback)
         load_symset("default", ROGUESET);
-    }
+
 #ifdef PDCURSES
     /* PDCurses for SDL, win32 and OS/2 has the ability to set the
        terminal size programatically.  If the user does not specify a