use MOVE_ARRAY

use MOVE_ARRAY

Simplify the code for moving members inside of an array and make it more
robust by using the helper macro MOVE_ARRAY.  It calculates the size
based on the specified number of elements for us and supports NULL
pointers when that number is zero.  Raw memmove(3) calls with NULL can
cause the compiler to (over-eagerly) optimize out later NULL checks.

This patch was generated with contrib/coccinelle/array.cocci and spatch
(Coccinelle).

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>