all: Remove trailing newlines from g_message()/g_warning()/g_error()s

All those logging functions already add a newline to any message they
print, so there’s no need to add a trailing newline in the message
passed to them.

Signed-off-by: Philip Withnall <withnall@endlessm.com>
Reviewed-by: nobody

tests/mainloop-test.c

@@ -203,7 +203,7 @@ io_pipe (GIOChannel **channels)
   if (pipe(fds) < 0)
     {
       int errsv = errno;
-      g_warning ("Cannot create pipe %s\n", g_strerror (errsv));
+      g_warning ("Cannot create pipe %s", g_strerror (errsv));
       exit (1);
     }