======Synopsis:======
[[on]] [<modes>]mode [<serial#>] [-|^]<match> { <action> }

======Description:======
This hook is triggered whenever the client observes a mode change on a
channel, or whenever the client changes its modes.

======Parameters:======
|$0    |nickname of person issuing mode change |
|$1    |channel or nickname affected by mode change |
|$2    |modes changed |
|$3-   |arguments to modes (if any) |

======Examples:======
To distinguish between user modes and channel modes:
   on ^mode "*" {
      if ( [$1] == N ) {
         xecho -b User mode change for $1: $2-
      } {
         xecho -b Mode change for $1 by $0: $2-
      }
   }