Use the m_grant from ircd-seven

Use the m_grant from ircd-seven

Charybdis' rewritten m_grant introduces at least one serious bug without
providing any apparent benefit. I think the best solution here is the
easiest one.

The bug in question is that an empty mode change is triggered after
seven's grant has done its work, and this is necessary in order to
give umodes granted by oper privileges a chance to update. The rewrite
removes this, generating a mode change only if it wants to change the
state of +o, which means the grant victim can keep privileged modes they
no longer have access to, or fail to gain new ones.