Added comment lines in French & Turkish which basically mean "Bitcoin, virtual P2P cryptocurrency".

contrib/debian/bitcoin-qt.desktop

@@ -2,6 +2,8 @@
 Encoding=UTF-8
 Name=Bitcoin
 Comment=Bitcoin P2P Cryptocurrency
+Comment[fr]=Bitcoin, monnaie virtuelle cryptographique pair à pair
+Comment[tr]=Bitcoin, eşten eşe kriptografik sanal para birimi
 Exec=/usr/bin/bitcoin-qt
 Terminal=false
 Type=Application