To libify the apply functionality the 'max_change' and 'max_len'
variables should not be static and global to the file. Let's move
them into 'struct apply_state'.
Reviewed-by: Stefan Beller <sbeller@google.com> Signed-off-by: Christian Couder <chriscool@tuxfamily.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>