Use _Static_assert to check macro lengths

[pguyot]

These changes are made under both the "Apache 2.0" and the "GNU Lesser General Public License 2.1 or later" license terms (dual license).

SPDX-License-Identifier: Apache-2.0 OR LGPL-2.1-or-later

[bettio]

I think we should just enable this on the right version of clang, and then merge it. It is useful and we are close to have it working.