internal: do not define boolean variables in C23

In C23, "true", "false", and "bool" are reserved keywords and cannot
be redefined:
https://en.wikipedia.org/wiki/C23_(C_standard_revision)#Keywords

Signed-off-by: Daiki Ueno <dueno@redhat.com>
Signed-off-by: Stephan Mueller <smueller@chronox.de>

Author: ueno

internal/api/bool.h

@@ -26,7 +26,7 @@ extern "C" {
 
 #ifndef LINUX_KERNEL
 
-#ifndef false
+#if defined(__STDC_VERSION__) && __STDC_VERSION__ < 202311L && !defined(false)
 /* Boolean variable */
 enum { false, true };
 typedef _Bool bool;