Add defvars for many vars already being used.

Add defvars for many vars already being used.
(emerge-options-menu, emerge-merge-menu, emerge-move-menu): New vars.
(emerge-setup-fixed-keymaps): Set up emerge-move-menu,
emerge-merge-menu and emerge-options-menu.  Put them into
emerge-fast-keymap.
(emerge-set-keys): Put them into the emerge-edit-keymap.
(emerge-minor-modes-list): Add defvar.
(emerge-before-flag, emerge-after-flag): Move defvars up.
(emerge-files-remote, emerge-files-with-ancestor-remote):
(emerge-remote-exit): Var exit-func renamed to emerge-exit-func.