Tidy up the alert-parsing code.

Align the DTLS and TLS implementations more. s3_pkt.c's version still has
remnants of fragmentable alerts and only one side marks some variables as
const. Also use warning/fatal constants rather than the numbers with comments.

Change-Id: Ie62d3af1747b6fe4336496c047dfccc9d71fde3f
Reviewed-on: https://boringssl-review.googlesource.com/3562
Reviewed-by: Adam Langley <agl@google.com>
2 files changed