release: update NEWS

NEWS

+=======================================================
+network-manager-applet-1.8.18
+Overview of changes since network-manager-applet-1.8.16
+=======================================================
+
+* libnma: fix wrongly showing hidden GUI elements, which
+  causes connection editing to behave wrong (issue#20).
+* libnma, c-e: fix translation issues in GUI due to missing
+  gettext domain (bgo#792285).
+* Update Croatian, German, Indonesian, Italian, Kazakh, and Turkish
+  translations.
+
 =======================================================
 network-manager-applet-1.8.16
 Overview of changes since network-manager-applet-1.8.14