[TxMt] i-search keybindings

[Damien Pollet]

> So basically if you hit an arrow key which will not make the cursor move
> within the search string it aborts.

IMHO this is a mode, eg the meaning of the arrow key will change
whether the cursor is in the search string or at an end. Moreover the
user focus is on the occurences hilighted in the file, rather than on
the field at the bottom of the window. Since that occurence is
selected, it seems coherent that the arrow keys would do what they
usually do: exit the selection. Also that behavior will be familiar to
Emacs users.

Fixing using backspace shouldn't be so much of a hassle since search
strings are typically short, and as the results are incrementally
displayed, the user can detect errors early.

-- D