fix: integer parsed as float when EINTR set in errno

[StuartGorman]

Problem: Occasionally the OS will set errno to EINTR if some system call has been interrupted. If that happens in lexer:scan_number() it will be treated the same as errno being set to ERANGE due to the check being errno == 0. This will cause valid integers to be parsed as floats.

Fix: Changing the errno check to explicitly check for ERANGE, as that is the condition that the parsing code cares about.

Environment:

• gcc (Ubuntu 11.4.0-1ubuntu1~22.04) 11.4.0
• cmake version 3.26.3

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• Changes are described in the pull request, or an existing issue is referenced.
• The test suite compiles and runs without error.
• Code coverage is 100%. Test cases can be added by editing the test suite.
• The source code is amalgamated; that is, after making changes to the sources in the include/nlohmann directory, run make amalgamate to create the single-header files single_include/nlohmann/json.hpp and single_include/nlohmann/json_fwd.hpp. The whole process is described here.

[nlohmann]

Please run the amalgamation with astyle 3.1.

[github-actions]

🔴 Amalgamation check failed! 🔴

The source code has not been amalgamated. @StuartGorman
Please read and follow the Contribution Guidelines.

[coveralls]

coverage: 100.0%. remained the same
when pulling 69c9fe0 on StuartGorman:bugfix/errno_restrict_to_erange
into 378e091 on nlohmann:develop.

[nlohmann]

Looks good to me.

[nlohmann]

Thanks!