Fix some miscellaneous MSVC warnings

[0xfadead]

Changes

• Added definition _CRT_SECURE_NO_WARNINGS to fix a warning related to strncpy().
• Excluded newer versions of MSVC on (old) line 139.
• Added (void) cond in cthreads_cond_destroy() because it isn't used.

Why

Because nobody likes compile-time warnings.

Checkmarks

• The modified functions have been tested. (MSVC 19.20)
• Used the same indentation as the rest of the project.

Additional information

[ThePedroo]

Looks awesome to me, just space changes. Thank you!

[ThePedroo]

Suggested change

	/* MSVC sees strncpy() as insecure. */
	#define _CRT_SECURE_NO_WARNINGS
	/* INFO: MSVC sees strncpy() as insecure. */
	#define _CRT_SECURE_NO_WARNINGS

[ThePedroo]

Also, is this widely compatible or affects files outside the project? For second case, I believe we can #undef it? Wouldn't be good to apply such for files outside.

[0xfadead]

I'm afraid there's no easy way to do this.
We could of course undef it, but it would still propagate because of windows.h's include guards.
The best solution would be to not require windows.h in the header, but the only way to do this is making all structs (or parts of structs using specific types) opaque.

I think the best course of action is just to remove the define and endur the warning or add an option for the user to disable the define.

[ThePedroo]

In my opinion we can should* strncpy for memcpy and just handle NULL terminator ending. With proper testing, it becomes safe anyway.

[0xfadead]

If I can find out in which version strncpy_s() was introduced, I could probably make it version dependent.