modes.h defines
#if defined(IRC_BAHAMUT) || defined(IRC_UNREAL)
# define CMODE_c 0x00000400 /* No ANSI colors in channel */
# define CMODE_O 0x00000800 /* Only opers can join channel */
#endif
However, in modes.c the code is:
#ifdef IRC_BAHAMUT
{ 'c', CMODE_c },
{ 'O', CMODE_O },
#endif
making them inaccessible to an Unreal build.