More font-lock improvements for diff-mode

More font-lock improvements for diff-mode

* lisp/vc/diff-mode.el (diff-font-lock-keywords): Use diff-header face
for git index lines (like already used for bzr index lines).
Use diff-file-header face for binary file headers.
(diff-find-source-location): Use expand-file-name for vc-find-revision.
(diff--font-lock-prettify): Use diff-indicator-* faces for
left-fringe indicators.
(diff-syntax-fontify-props): Optimize to not use text-property-not-all
for font-lock-ensure.

* lisp/replace.el (occur-engine-line): Simplify to use font-lock-ensure
without text-property-not-all.