
todo:
1) autobackup of things typed in.
	idea: each cell change output to a stdio open file
		in the save format, fflush() every so often...
		(diffs w/r to the original file)
2) lock/freeze (glue down) a section of the screen (the rest of the screen
	scrolls but a row/column/block stays fixed on the screen)
4) make sure ISVALID should <not> be used in place of checkbounds
	in interp.c
5) hide range
6) block moving into range
7) chain cells w/ equations into a linked list or dependency tree
	-have a top level eval, eval and UPDATE all lower nodes
8) an option to go into a ^R like <mode>
	++data entry fields (highlight entry cells)....
	++only allow entry in these cells....
10) don't redraw the whole screen all the time 
	(only cells that change, (in addition to what is in 'fixed #9'))
11) add uemacs keybinding stuff
12) add uemacs macro language
13) add uemacs command completion
15) on a Get if the buffer hasn't been written, ask to overwrite
16) add color capabilities.
