Update giflib to 5.1.1 (AOSP hash)

DEPS

Index: DEPS
diff --git a/DEPS b/DEPS
index 50707d450a0777ab24b5f56abbf7987685fcc895..28251d029d9108a95364164d79ee7b68a333bb4a 100644
--- a/DEPS
+++ b/DEPS
@@ -18,7 +18,7 @@ deps = {
   "third_party/externals/zlib"    : "https://chromium.googlesource.com/chromium/src/third_party/zlib@4ba7cdd0e7bf49d671645264f839838fc56e1492",
   # NOTE: If we update libpng, we may need to update the generated file at third_party/libpng/pnglibconf.h
   "third_party/externals/libpng"  : "https://skia.googlesource.com/third_party/libpng.git@070a616b8275277e18ef8ee91e2ca23f7bdc67d5",
-  "third_party/externals/giflib"  : "https://android.googlesource.com/platform/external/giflib.git@android-5.1.0_r3",
+  "third_party/externals/giflib"  : "https://android.googlesource.com/platform/external/giflib.git@ab10e256df4f684260ca239905b1cec727181f6c",
 
   "third_party/externals/libjpeg-turbo"             : "https://chromium.googlesource.com/chromium/deps/libjpeg_turbo.git@631e2dd119d49794e3572b6ca3f16ee39d59f372",
   # libjpeg-turbo depends on yasm to compile .asm files