Update Debian version and add translated links

wiki/src/doc/about/features.de.po

@@ -27,8 +27,8 @@ msgid "[[!toc levels=2]]\n"
 msgstr "[[!toc levels=2]]\n"
 
 #. type: Plain text
-msgid "Tails is based on [[Debian|https://www.debian.org/]] 8 (Jessie)."
-msgstr "Tails basiert auf [[Debian|https://www.debian.org/]] 8 (Jessie)."
+msgid "Tails is based on [[Debian|https://www.debian.org/]] 9 (Stretch)."
+msgstr "Tails basiert auf [[Debian|https://www.debian.org/index.de.html]] 9 (Stretch)."
 
 #. type: Title =
 #, no-wrap

wiki/src/doc/about/features.fr.po

@@ -27,10 +27,10 @@ msgid "[[!toc levels=2]]\n"
 msgstr "[[!toc levels=2]]\n"
 
 #. type: Plain text
-msgid "Tails is based on [[Debian|https://www.debian.org/]] 8 (Jessie)."
+msgid "Tails is based on [[Debian|https://www.debian.org/]] 9 (Stretch)."
 msgstr ""
-"Tails est basé sur [[Debian|https://www.debian.org/index.fr.html]] 8 "
-"(Jessie)."
+"Tails est basé sur [[Debian|https://www.debian.org/index.fr.html]] 9 "
+"(Stretch)."
 
 #. type: Title =
 #, no-wrap

wiki/src/doc/about/features.it.po

@@ -27,8 +27,8 @@ msgid "[[!toc levels=2]]\n"
 msgstr "[[!toc levels=2]]\n"
 
 #. type: Plain text
-msgid "Tails is based on [[Debian|https://www.debian.org/]] 8 (Jessie)."
-msgstr "Tails è basato su [[Debian|https://www.debian.org/]] 8 (Jessie)"
+msgid "Tails is based on [[Debian|https://www.debian.org/]] 9 (Stretch)."
+msgstr "Tails è basato su [[Debian|https://www.debian.org/index.it.html]] 9 (Stretch)"
 
 #. type: Title =
 #, no-wrap

wiki/src/doc/about/features.mdwn

@@ -2,7 +2,7 @@
 
 [[!toc levels=2]]
 
-Tails is based on [[Debian|https://www.debian.org/]] 8 (Jessie).
+Tails is based on [[Debian|https://www.debian.org/]] 9 (Stretch).
 
 Included software
 =================