kamailio SIP proxy: TLS broken

Description: Ubuntu 16.04 LTS
Release: 16.04

kamailio-tls-modules:
  Installed: 4.3.4-1.1ubuntu2
  Candidate: 4.3.4-1.1ubuntu2
  Version table:
 *** 4.3.4-1.1ubuntu2 990
        990 http://ubuntu.lagis.at/ubuntu xenial/universe amd64 Packages
        100 /var/lib/dpkg/status

hi,

kamailio does not work with TLS enabled. it seems to be an openssl problem as far as i have found out, but i didn't find any solution.

here is the error message that results when kamailio is started with an TLS enabled config:

Jun 13 12:13:20 xxx systemd[1]: Starting Kamailio (OpenSER) - the Open Source SIP Server...
Jun 13 12:13:20 xxx kamailio: ERROR: tls [tls_init.c:490]: tls_pre_init(): Unable to set the memory allocation functions
Jun 13 12:13:20 xxx kamailio: ERROR: <core> [sr_module.c:602]: load_module(): /usr/lib/x86_64-linux-gnu/kamailio/modules/tls.so: mod_register failed
Jun 13 12:13:20 xxx kamailio: : <core> [cfg.y:3432]: yyerror_at(): parse error in config file /etc/kamailio/kamailio.cfg, line 296, column 12-19: failed to load module
Jun 13 12:13:20 xxx kamailio: ERROR: <core> [modparam.c:150]: set_mod_param_regex(): No module matching <tls> found
Jun 13 12:13:20 xxx kamailio: : <core> [cfg.y:3435]: yyerror_at(): parse error in config file /etc/kamailio/kamailio.cfg, line 473, column 50: Can't set module parameter
Jun 13 12:13:20 xxx kamailio[26491]: ERROR: bad config file (2 errors)

the error message "Unable to set the memory allocation functions" results in a few google hits, for instance:
http://lists.sip-router.org/pipermail/sr-users/2013-August/079439.html

i have used ubuntu 12.04 LTS before and this is a complete reinstall (no upgrade). now my kamailio config does not work anymore as it did before.

i have also tried to install openssl from the following PPA (which i have been using on ubuntu 12 too) but it does not work either:
deb http://ppa.launchpad.net/ondrej/php/ubuntu xenial main
deb-src http://ppa.launchpad.net/ondrej/php/ubuntu xenial main