Don't add . to error message string

The norm is to have error strings without punctiation, so avoid adding
one as it just confuses the translators.

vncviewer/vncviewer.cxx

   } else {
     int result = mkdir(homeDir, 0755);
     if (result == -1 && errno != EEXIST)
-      vlog.error(_("Could not create VNC home directory: %s."), strerror(errno));
+      vlog.error(_("Could not create VNC home directory: %s"), strerror(errno));
     delete [] homeDir;
   }
 }