dnscrypt-proxy2: Update to 2.0.39

* Version 2.0.39
- The Firefox Local DoH service didn't properly work in version 2.0.38;
this has been fixed. Thanks to Simon Brand for the report!

* Version 2.0.38
- Entries from lists (forwarding, blacklists, whitelists) now support
inline comments.
- Reliability improvement: queries over UDP are retried after a timeout
instead of solely relying on the client.
- Reliability improvement: during temporary network outages, cached records
are now served even if they are stale.
- Bug fix: SOCKS proxies and DNS relays can be combined.
- New feature: multiple fallback resolvers are now supported (see the
new `fallback_resolvers` option. Note that `fallback_resolver` is
still supported for backward compatibility).
- Windows: the service can be installed with a configuration file
stored separately from the application.
- Security (affecting DoH): precompiled binaries of dnscrypt-proxy 2.0.37 are
built using Go 1.13.7 that fixes a TLS certificate parsing issue present in
previous versions of the compiler.

(nia)