add fuzzers from upstream

libwebp @ v1.1.0-37-g9f6055fc

animdecoder_fuzzer.cc isn't enabled as all of its dependencies are
imported currently; WebPAnimDecoder is unused by android.

fuzz_seed_corpus/ is a combination of:
  https://developers.google.com/speed/webp/gallery2
  https://chromium.googlesource.com/webm/libwebp-test-data
The files from the first are in the public domain, libwebp-test-data is
licensed the same as libwebp.

Bug: https://crbug.com/webp/409
Bug: 170243740
Change-Id: Ia4b890656ccc73d4d156b61f7e6a8477846abfc3
Test: builds for sargo-userdebug aosp_arm-eng aosp_arm64-eng aosp_x86-eng aosp_x86_64-eng aosp_crosshatch-userdebug
148 files changed