package/stunnel: bump to version 5.59

package/stunnel: bump to version 5.59

This release includes the following changes:

- Security bugfixes
  OpenSSL DLLs updated to version 1.1.1k.
- New features
  Client-side "protocol = ldap" support (thx to Bart Dopheide and Seth Grover).
- Bugfixes
  The test suite fixed not to require external connectivity.
  Fixed paths in generated manuals (thx to Tatsuki Makino).
  Fixed configuration reload when compression is used.
  Fixed compilation with early releases of OpenSSL 1.1.1.

Signed-off-by: Pierre-Jean Texier <texier.pj2@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>