Restore |BIO_f_base64| from OpenSSL at b4f0d1a, modulo style fixes.

Change-Id: Ia7f4f4f6d063d882cf3d3ac0f5f33ad8d8cd9875
Reviewed-on: https://boringssl-review.googlesource.com/5151
Reviewed-by: Adam Langley <agl@google.com>
4 files changed