* windmove.el (windmove-mode-map): Add special map for windmove commands.
(windmove-mode): Add minor mode for activating windmove-mode-map.
(windmove-install-defaults): Add general function for manipulating
windmove-mode-map.
(windmove-default-keybindings): Use windmove-install-defaults.
(windmove-display-default-keybindings): Use windmove-install-defaults.
(windmove-delete-default-keybindings): Use windmove-install-defaults.
(windmove-swap-states-default-keybindings): Use windmove-install-defaults.