Fix various mode-related bugs (including SF#2964782 and SF#2966959).

Fix various mode-related bugs (including SF#2964782 and SF#2966959).

src/chanserv.c (cmd_mode): Use MCP_NO_APASS, and unparse the mode
    change for display.
  (chan_opt_usergreeting): Use MCP_NO_APASS here too.
  (chanserv_conf_read): Likewise.
  (chanserv_channel_read): Likewise.

src/opserv.c (cmd_kick): Do not let users try to kick services.

src/proto.h (MCP_NO_APASS): New flag.

src/proto-p10.c (irc_user_mode_chars): Allow displaying +x.
  (mod_usermode): Treat +h as setting +x also.
  (mod_chanmode_parse): Reject +A and +U when passed MCP_NO_APASS.