Defeat various key repeating niggles.

Defeat various key repeating niggles.

Don't allow key repeating for unshifted keys and arrows.

Switch to pane left with ^p l.
Start typing ls.
Find yourself two panes left.

But allow control-alt-h/j/k/l to resize windows with repeats.

Using alt on its own doesn't work because terminal funkiness will lead
tmux to think, for example, alt-k was pressed if ^p^k is quickly followed
by escape then ^k.  This can (and does) happen when switching to a pane
and immediately recalling the previous history entry.