Jakob Unterwurzacher d9e89cd021 stupidgcm: use aead_seal for gcm as well
$ benchstat old.txt new.txt
name         old time/op   new time/op   delta
StupidGCM-4   7.87µs ± 1%   6.64µs ± 2%  -15.65%  (p=0.000 n=10+10)

name         old speed     new speed     delta
StupidGCM-4  520MB/s ± 1%  617MB/s ± 2%  +18.56%  (p=0.000 n=10+10)
2021-09-07 18:14:05 +02:00
..
2017-04-24 00:25:02 +02:00