Fixed clang compatibility

include/frg/std_compat.hpp

@@ -1,8 +1,10 @@
 #pragma once
+#include <cstddef>
 
 namespace frg {
 
 struct stl_allocator {
+#   ifndef __clang__
 	void *allocate(size_t size) {
 		return operator new(size);
 	}
@@ -13,7 +15,20 @@ struct stl_allocator {
 
 	void free(void *ptr) {
 		operator delete(ptr);
-	}
+    }
+#   else
+    void *allocate(size_t size) {
+        return operator new(size);
+    }
+
+    void deallocate(void *ptr, size_t size) {
+        operator delete(ptr);
+    }
+
+    void free(void *ptr) {
+        operator delete(ptr);
+    }
+#   endif
 };
 
 } // namespace frg