Fix compilation on OpenSUSE.

This patch fixes a build error with GCC 7.x which doesn't seem to accept
const int's as constants in macro initialization.

See: tpo/core/tor#40410
9 jobs for ahf/bug40410 in 14 minutes and 33 seconds (queued for 2 seconds)
latest
Status Name Job ID Coverage
  Test
passed debian-disable-dirauth #23936

00:05:41

passed debian-disable-relay #23937

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passed debian-distcheck #23932

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passed debian-docs #23933

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passed debian-hardened #23931

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passed debian-integration #23934

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passed debian-minimal #23930

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passed debian-nss #23938

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passed debian-tracing #23935

00:08:29