compat/atomics/gcc: use __typeof__ instead of typeof

The typeof keyword is apparently not available when using the -std=c99 option.

Fixes the use of C11 atomic functions with old GCC.
Reviewed-by: Muhammad Faiz <mfcc64@gmail.com>
Signed-off-by: James Almer <jamrial@gmail.com>

compat/atomics/gcc/stdatomic.h

@@ -100,8 +100,8 @@ do {                                    \
 
 #define atomic_exchange(object, desired)                            \
 ({                                                                  \
-    typeof(object) _obj = (object);                                 \
-    typeof(*object) _old;                                           \
+    __typeof__(object) _obj = (object);                             \
+    __typeof__(*object) _old;                                       \
     do                                                              \
         _old = atomic_load(_obj);                                   \
     while (!__sync_bool_compare_and_swap(_obj, _old, (desired)));   \
@@ -113,8 +113,8 @@ do {                                    \
 
 #define atomic_compare_exchange_strong(object, expected, desired)   \
 ({                                                                  \
-    typeof(object) _exp = (expected);                               \
-    typeof(*object) _old = *_exp;                                   \
+    __typeof__(object) _exp = (expected);                           \
+    __typeof__(*object) _old = *_exp;                               \
     *_exp = __sync_val_compare_and_swap((object), _old, (desired)); \
     *_exp == _old;                                                  \
 })