git-diff: fix combined diff
git-diff: fix combined diff

The code forgets that typecast binds tighter than addition, in
other words:

    (cast *)array + i  === ((cast *)array) + i

Signed-off-by: Johannes Schindelin <b4cf3b77c95aaa57254d96e276bf14cfc9472402@gmx.de>
Signed-off-by: Junio C Hamano <dc50d1021234060e53ec42a77d526afa2fe07479@cox.net>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git