Print the name of the function KEY invokes. KEY is a string.
If INSERT (the prefix arg) is non-nil, insert the message in the buffer.
If non-nil, UNTRANSLATED is a vector of the untranslated events.
It can also be a number in which case the untranslated events from
the last key hit are used.
If KEY is a menu item or a tool-bar button that is disabled, this command
temporarily enables it to allow getting help on disabled items and buttons.