Split test-unicode to avoid timeouts

[nickaein]

This PR splits the long-running unit-test_all into two standalone unit-tests.

Fixes #1816, fixes #1032 (hopefully).

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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.
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Please don't

• The C++11 support varies between different compilers and versions. Please note the list of supported compilers. Some compilers like GCC 4.7 (and earlier), Clang 3.3 (and earlier), or Microsoft Visual Studio 13.0 and earlier are known not to work due to missing or incomplete C++11 support. Please refrain from proposing changes that work around these compiler's limitations with #ifdefs or other means.
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[coveralls]

Coverage remained the same at 100.0% when pulling 9b0a3e6 on nickaein:fix/split-unicode-tests into bde5712 on nlohmann:develop.

[nickaein]

@nlohmann

What do you think of this simple re-organization for test-unicode to partition its running time that could help fix issues like #1816 and #1032.

The pipeline has falied due to (ironically) exceeding Appveyor 1 hour limit. A re-run might fix that.

I've also tried to some micro-optimizations on implementation of check_utf8dump and check_utf8string but didn't find a significant improvement (yet).

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[dota17]

@nickaein
Currently, the test-unicode_all is always not finished because times out.
This often happens in Xcode 9.2 C++ and before.

I think this PR is a good try. We can reopen this one to solve the problem.

[nickaein]

@dota17 Can you test this branch locally to see whether it is effective in your case?

https://github.com/nickaein/nlohmann-json/tree/fix/split-unicode-tests

[nlohmann]

Can you please update to the latest develop branch - there have been several fixes with respect to the CI.

[dota17]

Can you test this branch locally to see whether it is effective in your case?
https://github.com/nickaein/nlohmann-json/tree/fix/split-unicode-tests

Everything is fine in my local env.
It should be verified in this repo's travis-ci and currently, i had not find any error.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.