Tk::DropSite - Receive side of Drag & Drop abstraction
use Tk::DropSite qw(...);
$widget->DropSite(-entercommand => ...,
-dropcommand => ...,
-motioncommand => ...,
-dropcommand => ...,
);
DropSite creates an object which represents a site on which things
may be "Dropped".
A DropSite provides the following methods: