stdatomic.h: add atomic definitions for char8_t, char16_t and char32_t

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

Author: github-cygwin

newlib/libc/include/stdatomic.h

@@ -54,6 +54,9 @@
 #ifdef __GCC_ATOMIC_CHAR_LOCK_FREE
 #define	ATOMIC_CHAR_LOCK_FREE		__GCC_ATOMIC_CHAR_LOCK_FREE
 #endif
+#if __ISO_C_VISIBLE >= 2020 && defined(__GCC_ATOMIC_CHAR8_T_LOCK_FREE)
+#define ATOMIC_CHAR8_T_LOCK_FREE        __GCC_ATOMIC_CHAR8_T_LOCK_FREE
+#endif
 #ifdef __GCC_ATOMIC_CHAR16_T_LOCK_FREE
 #define	ATOMIC_CHAR16_T_LOCK_FREE	__GCC_ATOMIC_CHAR16_T_LOCK_FREE
 #endif
@@ -199,10 +202,11 @@ typedef _Atomic(long)			atomic_long;
 typedef _Atomic(unsigned long)		atomic_ulong;
 typedef _Atomic(long long)		atomic_llong;
 typedef _Atomic(unsigned long long)	atomic_ullong;
-#if 0
-typedef _Atomic(__char16_t)		atomic_char16_t;
-typedef _Atomic(__char32_t)		atomic_char32_t;
+#if __ISO_C_VISIBLE >= 2020
+typedef _Atomic(unsigned char)          atomic_char8_t;
 #endif
+typedef _Atomic(__char16_t)             atomic_char16_t;
+typedef _Atomic(__char32_t)             atomic_char32_t;
 typedef _Atomic(wchar_t)		atomic_wchar_t;
 typedef _Atomic(int_least8_t)		atomic_int_least8_t;
 typedef _Atomic(uint_least8_t)		atomic_uint_least8_t;