Scott D Phillips authored Nov 28, 2016 and Sebastian Dröge committed Dec 05, 2016

For pre-1.1.x openssl, a callback to set the thread id needs to be
provided to openssl. In 0.9.x the thread id was an unsigned long. In
1.0.x it was expanded to be able to hold a void*. Here we change to use
the 1.0.x API so that the thread id can always hold a GThread*, even on
platforms like msvc x64 where unsigned long is only 32 bits.

All of this is still #ifdef'd out of existence when building with
openssl 1.1.x or later which changed the thread API again, and does not
need a thread id callback.

https://bugzilla.gnome.org/show_bug.cgi?id=775292