external/boringssl: Sync to 171b54.

This includes the following changes:

https://boringssl.googlesource.com/boringssl/+log/8ca0b4127da11d766067ea6ec4122017ba0edb0e..171b5403ee767fa0f3aecd377867db6533c3eb8f

This also updates the build file to build as C99, so BoringSSL can use
variables in for loops.

Change-Id: I48ae985fd1bed244f7ed327aefc9a13e5b17b185
101 files changed