Rather than four massive functions that handle every extension,
organise the code by extension with four smaller functions for each.
Change-Id: I876b31dacb05aca9884ed3ae7c48462e6ffe3b49
Reviewed-on: https://boringssl-review.googlesource.com/5142
Reviewed-by: Adam Langley <agl@google.com>
614c66a2f8