more colortable[] updates

declare colortable[] const and no longer static so it can be shared
by code in window ports..

get rid of the Windows console port rgbtable and use the
core colortable[] instead.

utilize function colortable_to_int32() in Windows console instead
of the rgbtable_to_long() in the Windows port.

delete the Windows rgbtable_to_long() function.

include/color.h

@@ -72,6 +72,8 @@ typedef struct color_and_attr {
            int color, attr;
 } color_attr;
 
+extern const struct nethack_color colortable[];
+
 #endif /* COLOR_H */
 
 /*color.h*/