make `+rb $~a` prioritise ERR_NEEDREGGEDNICK

[jesopo]

rationale is that prioritising the version that gives the most information about the reason for not being able to join is a good idea, though this makes less sense for +rb nick!*@* when your nick is nick, but you'd still have to address both reasons for not being able to join in any case.

one could argue this should instead be solved by -b $~a but i can imagine people unintentionally having both set or wanting the fallback or whatever, and prioritising +r might lead to fewer confused users.

I assume this is as simple as moving

charybdis/ircd/channel.c

Lines 736 to 737 in 9dd128b

	if(chptr->mode.mode & MODE_REGONLY && EmptyString(source_p->user->suser))
	i = ERR_NEEDREGGEDNICK;

above

charybdis/ircd/channel.c

Line 694 in 9dd128b

if((is_banned(chptr, source_p, NULL, &ms, forward)) == CHFL_BAN)