UI|Client: Minor improvements

Don't warn about known shared libs not being plugins. Don't allow
negative time values in the "last updated since" string.

doomsday/apps/client/src/dd_plugin.cpp

@@ -103,6 +103,14 @@ static int loadPlugin(void * /*libraryFile*/, char const *fileName, char const *
     ::Library *plugin = Library_New(pluginPath);
     if(!plugin)
     {
+#ifdef UNIX
+        String const fn = Path(pluginPath).fileName();
+        if(fn.contains("libfmodex") || fn.contains("libassimp"))
+        {
+            // No need to warn about these shared libs.
+            return 0;
+        }
+#endif
         LOG_RES_WARNING("Failed to load \"%s\": %s") << pluginPath << Library_LastError();
         return 0; // Continue iteration.
     }

doomsday/apps/client/src/updater/updatersettings.cpp

@@ -171,6 +171,7 @@ de::String UpdaterSettings::lastCheckAgo() const
     if(!when.isValid()) return ""; // Never checked.
 
     de::TimeDelta delta = when.since();
+    if(delta < 0.0) return "";
 
     int t;
     if(delta < 60.0)