History Pane
------------
	This pane is invoked from the "History" menu item.  It is opened
by selecting view history, and may be closed by clicking on the quit button.
If the window gets lost on your display, it is probably easiest to just
close and reopen the window from the menu (a number of history elements, 
as indicated in the history menu, will be saved).
Clicking on any item with the left button goes to that history event,
by a call to historySelectBind


Implementation
--------------
	The functions that implement this pane are found in the source file
browserHistory.tcl.  

Functions
---------
historyCreate
	Creates the history window as a text window,
gHistoryFrame. Checks the variable gHistoryList,and if it is not
empty, inserts the elements into the history box

historyAdd
	Whenever a class or function is visited, addHistory is called
with the required information. The information is stored in
gHistoryList as well as being added to the history window if it is
visible.  Called from textShowClassDef (visit a class - update the
text and feature list windows) and textUpdateFeatureView (visit a
feature - update text window)

private historyInit
	Add all elements from gHistoryList to the list window. Called by
create

private historySelectBind
	Ignores arguments. Selects the element under the cursor click.
Splits the list into components and then sends the browser to that spot.

historyQuit
	Unmap the history window (but retain history list)

Globals
-------
gHistoryFrame	Main history window frame (toplevel). look at createHistory
		to see names of parts (main list is ${gHistoryFrame}.l)
gHistoryList	Holds history elements
gHistoryLimit	Maximum number of elements stored in the list