stun: Fix LibreSSL support

Closes #71
6 jobs from master in 5 minutes and 50 seconds (queued for 11 seconds)
Status Job ID Name Coverage
  Build
passed #119783
build autotools

00:00:49

passed #119784
build meson

00:00:22

 
  Test
passed #119786
distcheck autotools

00:02:09

passed #119788
doc-and-install meson

00:00:35

passed #119785
test autotools

00:01:19

passed #119787
allowed to fail
test meson

00:00:35