stun: Fix LibreSSL support

Closes #71
6 jobs for <span class="ref-name">libressl</span> in 7 minutes and 4 seconds (queued for 2 minutes)
Status Job ID Name Coverage
  Build
passed #119706
build autotools

00:01:03

passed #119707
build meson

00:00:30

 
  Test
passed #119709
distcheck autotools

00:02:24

passed #119711
doc-and-install meson

00:00:49

passed #119708
test autotools

00:01:33

passed #119710
allowed to fail
test meson

00:00:42