feat(headers): stddef/stdint/stdbool/limits/float/assert + features wiring

include/stdbool.h

@@ -0,0 +1,27 @@
+#ifndef VLIBC_STDBOOL_H
+#define VLIBC_STDBOOL_H
+
+/*
+ * vlibc — <stdbool.h>.
+ *
+ * In C23 bool, true and false are keywords, so this header defines only the
+ * guard macro __bool_true_false_are_defined. In C17 (and older) it defines
+ * the _Bool-based spellings the standard requires. In C++ the three names are
+ * keywords as well, so only the guard macro is defined there too.
+ *
+ * This header is ISO C core and is present in every profile.
+ */
+
+#include <vlibc/features.h>
+
+#ifndef __cplusplus
+#if !defined(__STDC_VERSION__) || __STDC_VERSION__ < 202311L
+#define bool _Bool
+#define true 1
+#define false 0
+#endif
+#endif
+
+#define __bool_true_false_are_defined 1
+
+#endif /* VLIBC_STDBOOL_H */