2.28 only: build broken when check_config.h is not included

[gilles-peskine-arm]

In Mbed TLS 2.x, including mbedtls/check_config.h is optional. We do it in the default configuration file, but users can provide their own configuration file that doesn't include it.

The general philosophy of check_config.h is to have no side effects, but that's not completely true:

• On Windows (#if defined(_WIN32)), it might define MBEDTLS_PLATFORM_SNPRINTF_ALT and MBEDTLS_PLATFORM_VSNPRINTF_ALT.
• It includes limits.h.

We need to ensure that these side effects don't matter. They do as of Mbed TLS 2.28.7: at least oid.c uses UINT_MAX but does not include limits.h, which breaks the build when check_config.h is not included. See openthread/openthread#10263 (comment)

This is not an issue in Mbed TLS ≥3.0 because there check_config.h has no side effects: the side effects happen in build_info.h.

Almost all of our CI builds (if not all?) include check_config.h. So we might not notice if a build breaks when check_config.h is not included. The goal of this issue is to:

• Do a build with check_config.h omitted in all.sh.
• Fix oid.c and any other problem.
• What about the Windows (v)snprintf alt stuff?

[gilles-peskine-arm]

Resolved by #9153