[c_api] Improve ANSI compatibility by avoiding <stdbool.h>

[drewmiller]

Mentioned in #4609, these edits improve ANSI C compatibility by removing reliance on stdbool.h. These edits may cause a compiler warning for existing code which passes a _Bool pointer as out. However, given the brief tenure of ANSI C compatibility, it seems unlikely there will be much breakage.

[StrikerRUS]

LGTM, thanks a lot for your contribution!

[shiyu1994]

Shall we change the call of LGBM_BoosterGetLinear in basic.py?

LightGBM/python-package/lightgbm/basic.py

Lines 3569 to 3572 in dc02dca

	out_is_linear = ctypes.c_bool(False)
	_safe_call(_LIB.LGBM_BoosterGetLinear(
	self.handle,
	ctypes.byref(out_is_linear)))

Since _Bool may have smaller size than int, it seems that we can wrongly set some unallocated bytes when calling LGBM_BoosterGetLinear.

[StrikerRUS]

Shall we change the call of LGBM_BoosterGetLinear in basic.py?

Ah, indeed, we definitely should! Sorry, I missed this one call of LGBM_BoosterGetLinear across the whole LightGBM codebase.

@drewmiller Could you please update the linked Python code or do you need any help with it?

[StrikerRUS]

Kindly ping @drewmiller

[drewmiller]

Kindly ping @drewmiller

Apologies for the delay. Will make the change this weekend.

[StrikerRUS]

No problem, please take your time. I just wanted to make sure you didn't forget about this PR.

[jameslamb]

Thanks @drewmiller !

[github-actions]

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