libidn and fix for ghostscript passwords

The new ghostscript could not decrypt some password protected files. It turned out to be a bug in ghostscript but in the process of investigating I thought it might be related to missing libidn that is also used in PDF passwords, so I added it.

See merge request !1455
13 jobs for feat/slapos_testing_python3_new in 0 seconds
Status Job ID Name Coverage
  External
passed ERP5.StandaloneDeploymentScriptTest-Debian.Buster

00:40:56

failed ERP5.StandaloneDeploymentScriptTest-Debian.Buster.Master

15:02:23

passed SlapOS-Master.StandaloneDeploymentScriptTest-Debian.Buster

00:35:49

passed SlapOS.SoftwareReleases.IntegrationTest-Master

failed SlapOS.Theia.ResilienceTest-Master-ERP5

passed Wendelin.StandaloneDeploymentScriptTest-Debian.Buster

00:29:23

failed Wendelin.StandaloneDeploymentScriptTest-Debian.Buster.Master

15:02:20

passed ERP5.StandaloneDeploymentScriptTest-Debian.Buster

failed ERP5.StandaloneDeploymentScriptTest-Debian.Buster.Master

passed SlapOS-Master.StandaloneDeploymentScriptTest-Debian.Buster

passed Wendelin.StandaloneDeploymentScriptTest-Debian.Buster

00:30:13

failed Wendelin.StandaloneDeploymentScriptTest-Debian.Buster.Master

failed Wendelin.StandaloneDeploymentScriptTest-Debian.Buster.Master

15:02:12