(vi-join-lines): Locally bind count.

(vi-join-lines): Locally bind count.
(vi-search-forward, vi-search-backward): Use isearch-update-ring.
(vi-repeat-last-search, vi-reverse-last-search):
Get string from the ring.
(vi-mode-old-major-mode, vi-mode-old-mode-name): New defvars.
(vi-mode-old-local-map, vi-mode-old-case-fold): Likewise.
(vi-tilde-map): Move the defvar and bindings to the front.