(cua--rectangle-padding): Remove.

(cua--rectangle-padding): Remove.
(cua--rectangle-virtual-edges): New defun.
(cua--rectangle-get-corners): Remove optional PAD arg.
(cua--rectangle-set-corners): Never do padding.
(cua--forward-line): Remove optional PAD arg.  Simplify.
(cua-resize-rectangle-right, cua-resize-rectangle-left)
(cua-resize-rectangle-down, cua-resize-rectangle-up):
(cua-resize-rectangle-bot, cua-resize-rectangle-top)
(cua-resize-rectangle-page-up, cua-resize-rectangle-page-down)
(cua--rectangle-move): Never do padding.  Simplify.
(cua--tabify-start): New defun.
(cua--rectangle-operation): Add tabify arg.  All callers changed.
(cua--pad-rectangle): Remove.
(cua--delete-rectangle): Handle delete with virtual edges.
(cua--extract-rectangle): Add spaces if rectangle has virtual edges.
(cua--insert-rectangle): Handle insert at virtual column.
Perform auto-tabify if necessary.
(cua--activate-rectangle): Remove optional FORCE arg.
Never do padding.  Simplify.
(cua--highlight-rectangle): Enhance for virtual edges.
(cua-toggle-rectangle-padding): Remove command.
(cua-toggle-rectangle-virtual-edges): New command.
(cua-sequence-rectangle): Add optional TABIFY arg.  Callers changed.
(cua--rectangle-post-command): Don't force rectangle padding.
(cua--init-rectangles): Bind M-p to cua-toggle-rectangle-virtual-edges.