Prepare for BoringSSL update.

This change tweaks things as needed so that the code will compile
against both the BoringSSL that's currently in Android and a version
from upstream. The BORINGSSL_201509 define is temporary to allow the
switch to happen without breaking the build and a followup change will
remove it.

Change-Id: Ia4df39a42eac403f0ce63a55b511db1b8ac40942
1 file changed