Fix build error under non-Clang compilers

Author: sylveon

include/rapidjson/internal/clzll.h

@@ -29,7 +29,7 @@
 RAPIDJSON_NAMESPACE_BEGIN
 namespace internal {
 
-#if defined(__has_builtin) && __has_builtin(__builtin_clzll)
+#if (defined(__GNUC__) && __GNUC__ >= 4) || RAPIDJSON_HAS_BUILTIN(__builtin_clzll)
 #define RAPIDJSON_CLZLL __builtin_clzll
 #else
 

include/rapidjson/rapidjson.h

@@ -490,6 +490,12 @@ RAPIDJSON_NAMESPACE_END
 #define RAPIDJSON_VERSION_CODE(x,y,z) \
   (((x)*100000) + ((y)*100) + (z))
 
+#if defined(__has_builtin)
+#define RAPIDJSON_HAS_BUILTIN(x) __has_builtin(x)
+#else
+#define RAPIDJSON_HAS_BUILTIN(x) 0
+#endif
+
 ///////////////////////////////////////////////////////////////////////////////
 // RAPIDJSON_DIAG_PUSH/POP, RAPIDJSON_DIAG_OFF