ssl-utils: add missing ett registration

Fixes the dissector bug warning:
"epan/proto.c:4657: failed assertion "idx >= 0 && idx < num_tree_types"

Add some comments to avoid future mistakes, add folding markers and fix
alignment of curves hf.

Change-Id: Ibcb57bfeb09a9777324682704a86f1ce260d345e
Reviewed-on: https://code.wireshark.org/review/2642
Reviewed-by: Alexis La Goutte <alexis.lagoutte@gmail.com>
(cherry picked from commit 4224e353f9ca3a3224ad2be3728905e729e74b9c)
Reviewed-on: https://code.wireshark.org/review/2817
Reviewed-by: Hauke Mehrtens <hauke@hauke-m.de>
Reviewed-by: Anders Broman <a.broman58@gmail.com>