Sync-patch with libwebp ver 0.4.1-rc1.

Sync-patch with libwebp ver 0.4.1-rc1 (change#I5346984d2).
  - NEON assembly optimizations:
    - ~25% faster lossy decode / encode (-m 4)
    - ~10% faster lossless decode
    - ~5-10% faster lossless encode (-m 3/4)
  - Arch64 (arm64) & MIPS support/optimizations.

Change-Id: I855b65cec8fad5ec567c276b698e7714dc4bffd2
diff --git a/src/Android.mk b/src/Android.mk
index 6e1705b..90303ca 100644
--- a/src/Android.mk
+++ b/src/Android.mk
@@ -26,22 +26,31 @@
         enc/frame.c\
         enc/histogram.c \
         enc/iterator.c \
-        enc/layer.c \
         enc/picture.c \
+        enc/picture_csp.c \
+        enc/picture_psnr.c \
+        enc/picture_rescale.c \
+        enc/picture_tools.c \
         enc/quant.c \
         enc/syntax.c \
         enc/tree.c \
         enc/token.c \
         enc/vp8l.c \
         enc/webpenc.c \
+        dsp/alpha_processing.c \
         dsp/cpu.c \
         dsp/cpu-features.c \
         dsp/enc.c \
+        dsp/enc_avx2.c \
+        dsp/enc_mips32.c \
         dsp/enc_neon.c \
         dsp/enc_sse2.c \
         dsp/lossless.c \
+        dsp/lossless_mips32.c \
+        dsp/lossless_neon.c \
+        dsp/lossless_sse2.c \
         dsp/yuv.c \
-        utils/alpha_processing.c \
+        dsp/yuv_sse2.c \
         utils/bit_writer.c \
         utils/color_cache.c \
         utils/filters.c \
@@ -74,24 +83,30 @@
         dec/frame.c \
         dec/idec.c \
         dec/io.c \
-        dec/layer.c \
         dec/quant.c \
         dec/tree.c \
         dec/vp8.c \
         dec/vp8l.c \
         dec/webp.c \
+        dsp/alpha_processing.c \
         dsp/cpu.c \
         dsp/cpu-features.c \
         dsp/dec.c \
+        dsp/dec_clip_tables.c \
+        dsp/dec_mips32.c \
         dsp/dec_neon.c \
         dsp/dec_sse2.c \
         dsp/lossless.c \
+        dsp/lossless_mips32.c \
+        dsp/lossless_neon.c \
+        dsp/lossless_sse2.c \
         dsp/upsampling.c \
         dsp/upsampling_neon.c \
         dsp/upsampling_sse2.c \
         dsp/yuv.c \
+        dsp/yuv_mips32.c \
+        dsp/yuv_sse2.c \
         demux/demux.c \
-        utils/alpha_processing.c \
         utils/bit_reader.c \
         utils/color_cache.c \
         utils/filters.c \