[REQ]Cpp14 compliance

[d-wang03]

Describe the new feature

Since the cpp14 is used more widely especially on embedded devices, I suggest make the thread pool to compliant with it.
Here is the patch, that I tried to port the thread pool lite, and get no errors and all test cases in BS_thread_pool_light_test.cpp passed.
Could you review it, and merge it in future?
cpp14.patch

[bshoshany]

Thanks for the suggestion! However, the title of the project is "BS::thread_pool: a fast, lightweight, and easy-to-use C++17 thread pool library". Therefore, it is only meant to be compatible with C++17 or later. I do not have any plans to make it backwards-compatible with C++14 or older versions, now or in the future. Your patch might work (although I haven't tested it), but it makes the code longer and less elegant, and in the future I might want to use other C++17 features that cannot be backported like this.

You are, of course, more than welcome to use your C++14 version for your own needs, or even create your own fork that is C++14 compatible.