Purpose: define what a megawidget is, and point to various discussions relating to megawidgets on the wiki.
A megawidget is a widget that is implemented in Tcl, not in C. It should behave according to the principles set out by the standard Tk widgets, being able to be manipulated by invoking methods on its pathname, being constructed in the standard way, supporting options through configure and cget methods, participating in geometry management, focus traversal, event handling, etc.