dec_neon: DC4: use pair-wise adds for top row

reduces load count, slightly faster

Change-Id: I880340ef8ef75ce4ce321c330f56f86b758bda08
dsp/dec_{neon,sse2}: VE4: normalize variable names

use '0' rather than '_' when dealing with variables that result from a
shift

Change-Id: I29280c0dead645ce39dc4bb42c3e19929b302fd4
Merge "dsp/dec_{neon,sse2}: VE4: normalize variable names"
Merge "dec_neon: DC4: use pair-wise adds for top row"
update NEWS

Change-Id: Ib9b48e3611b77214bc875524249366ff62451c1b
(cherry picked from commit 0c1b98d28c1dec2ea45c101fca979b31b8db1e5b)