* helm.el (helm--window-side-state): New, use it to restore helm-window on last used side after swapping or toggling.
(helm-window-side-state): New flag, internal.
(helm-initial-setup): reset helm-window-side-state.
(helm-display-buffer, helm-toggle-resplit-window
helm-swap-windows): Set helm-window-side-state with helm--window-side-state fn.
* helm.el (helm--window-side-state): Renamed from helm-window-side-state (internal var).
(helm--get-window-side-state): Renamed from helm--window-side-state (function).