* lisp/vc/emerge.el: Use lexical-binding

* lisp/vc/emerge.el: Use lexical-binding

Replace all `(lambda ...) with closures.  Use inhibit-read-only.
(emerge-mode): Use define-minor-mode.
(emerge-setup, emerge-setup-with-ancestor):
Don't use 'run-hooks' on local var.
(emerge-files, emerge-files-with-ancestor):
Don't use 'add-hook' on local var.
(emerge-convert-diffs-to-markers): Remove unused var 'B-point-min'.
Simplify 'offset'.
(emerge--current-beg, emerge--current-end): New macros.
(emerge-select-version): Pass 'diff-vector' to the function it calls.
Change all callers to use it instead of dyn-bound vars.