Implement operspy for /list. Normally hidden channels are prefixed with a !

atheme/charybdis/bb55ebebe997ccf503fda4a26936e10f18fb8723 : Implement operspy for /LIST.
atheme/charybdis/bf0a45920d6ef4d39f46b3923a03d3a89fcf4972 : modules/m_list.c: Change operspy LIST syntax to match everything else that accepts operspy.
atheme/charybdis/a4eeda898e06362535494b4dfa1b163ecf8eb9bb : operspy list: Show '!' prefix for otherwise hidden channels rather than +s ones. This is consistent with operspy whois.