Group ALPN functions into their own section.

These were already documented, though some of the documentation was
expanded on slightly.

Change-Id: I04c6276a83a64a03ab9cce9b9c94d4dea9ddf638
Reviewed-on: https://boringssl-review.googlesource.com/5896
Reviewed-by: Adam Langley <agl@google.com>
2 files changed