make bifilter4_coeff[][] uint8_t, no values exceed this range and
they're loaded with vdup_n_u8().
Change-Id: I921983e9edd828d29820e40ac30a7801dbe0fb4f
Filter out files ending in _neon.c and append .neon so the Android build
system knows to apply -mfpu=neon
Change-Id: Ib67277e5920bfcaeda7c4aa16cd1001b11d59305