external/webp: update to v1.0.2

general lossless encoder and NEON lossy encoder speedups

Test: aosp_arm-eng aosp_arm64-eng aosp_x86-eng aosp_x86_64-eng
      aosp_crosshatch-userdebug build

Change-Id: Idd838fb8dcdadf50e0def2b46c6658b0b34c6417
19 files changed