Create new release (version 13)

Change meson.build to include new release, that
will contain latest fixes in tang repository

Resolves: latchset#112

Proposed changelog:

socket: fix possible buffer overflow in listen_port() (#9b9d149)
socket: free socket list before exiting (#5631569)
tests: make sure on_exit handler completes (#0cacc91)
tests: fix wait_for_port() retry mechanism (#5160a4a)
use sigaction instead of signal for SIGCHLD processing (#f44f4ec)
tangd.socket: Set ownership and mode of jwkdir (#ae736c9)

Signed-off-by: Sergio Arroutbi <sarroutb@redhat.com>

meson.build

@@ -1,5 +1,5 @@
 project('tang', 'c',
-  version: '12',
+  version: '13',
   license: 'GPL3+',
   default_options: [
     'c_std=c99',