external/boringssl: Sync to f8de2af7e319f83ba88579fbf127ba5fafc26c71.

This includes the following changes:

https://boringssl.googlesource.com/boringssl/+log/73ffb74b9e36a93a3e593010a367a610105da9a1..f8de2af7e319f83ba88579fbf127ba5fafc26c71

Change-Id: Iab4fb4fde30c1f26ad2b98160abca366bdea1da4
Test: BoringSSL CTS Presubmits.
diff --git a/sources.bp b/sources.bp
index f303217..4a27ea6 100644
--- a/sources.bp
+++ b/sources.bp
@@ -386,6 +386,7 @@
         "src/crypto/asn1/asn1_test.cc",
         "src/crypto/base64/base64_test.cc",
         "src/crypto/bio/bio_test.cc",
+        "src/crypto/buf/buf_test.cc",
         "src/crypto/bytestring/bytestring_test.cc",
         "src/crypto/chacha/chacha_test.cc",
         "src/crypto/cipher_extra/aead_test.cc",