Fix msvc warnings

[MBalszun]

This PR:

1. Changes the accumulation variable for size computations in binar_writer from unsiged long to size_t [*]
2. Remove two warning suppressions in msvc for warnings that seem to no longer appear anyway (waiting for CI results to verify [EDIT: Can confirm no new warnings appeared in CI])

*) In the x64 platofrm on windows std::size_t (64 bit unsigned integer) is not the same as an unsigned long (32bit unsigned integer on all platforms targets). This leads to a (correct) warning about possible loss of data. I'm not sure if there is an actual situation, where this variable can overflow, but the warning itself needs to be fixed anyway and I believe the intent was to use a variable of type std::size_t (which is the same as unsigned long on almost all other platforms) anyway.

[EDIT: ] If preferred, I can split up the PR into one for 1. and 2.

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Pull request checklist

Read the Contribution Guidelines for detailed information.

• 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 file single_include/nlohmann/json.hpp. The whole process is described here.

[coveralls]

Coverage remained the same at 100.0% when pulling 25e0175 on Mike-Bal:fix_warnings into e7b3b40 on nlohmann:develop.

[nlohmann]

Looks good to me.

[nlohmann]

Thanks!

[nlohmann]

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🔖 Release item

This issue/PR will be part of the next release of the library. This template helps preparing the release notes.

Type

• ✨ New Feature
• 🐛 Bug Fix
• ⚡️ Improvement
• 🔨 Further Change
• 🔥 Deprecated function

Description

• An MSVC warning has been fixed which no longer needs to be suppressed when compiling the test suite. Fix msvc warnings #1846

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[MBalszun]

Thanks for the quick merge.

Just a comment on the release item description: The warning that was fixed and the warnings that got suppressed where independent of each other i.e. the warnings about possible loss of data popped up even with the suppression still active and removing the suppression would not pop up any new warnings either way. As the suppressions only existed in unit tests, I don't think they need to be mentioned in the release item description.

Sorry for putting them into one PR.

[nlohmann]

I see. What would you propose as alternative items for the release notes?

[MBalszun]

Would have to look at your previous notes for reference (i.e. not sure, what the typical level of detail is).

Probably something like either "Fix warning about possible loss of data on windows x64" or "Fix integer type mismatch in binary_writer size computation on windows x64"