vi: fix backspace over tab in commands

Colon and search commands are entered on the status line.  Since
the cursor position wasn't being tracked backspacing over a tab
resulted in a mismatch between the actual and apparent content
of the command.

function                                             old     new   delta
get_input_line                                       178     180      +2
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/0 up/down: 2/0)                 Total: 2 bytes

Signed-off-by: Ron Yorston <rmy@pobox.com>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>
1 file changed