cmake: add gettext support

cmake/gettext.cmake

@@ -0,0 +1,22 @@
+SET(languages de en fr nb nn pl pt_BR sv zh_CN)
+
+INCLUDE(FeatureSummary)
+
+OPTION(WITH_GETTEXT "translate messages if gettext is available" ON)
+IF(WITH_GETTEXT)
+  FIND_PACKAGE(Intl)
+  FIND_PACKAGE(Gettext)
+  IF(GETTEXT_FOUND)
+      SET(HAVE_GETTEXT 1)
+  ENDIF()
+ENDIF()
+ADD_FEATURE_INFO(gettext GETTEXT_FOUND "translate messages with gettext")
+
+# Define translations
+IF(GETTEXT_FOUND)
+  FOREACH(lang ${languages})
+    GETTEXT_PROCESS_PO_FILES(${lang} ALL
+                             INSTALL_DESTINATION ${CMAKE_INSTALL_FULL_LOCALEDIR}
+                             PO_FILES po/${lang}.po)
+  ENDFOREACH()
+ENDIF()