Revert of [regexp] Remove IsRegExp intrinsic

src/js/macros.py

Index: src/js/macros.py
diff --git a/src/js/macros.py b/src/js/macros.py
index 8b1462b240f8012ef16be008eca3c3fe2889992d..9fb665def7c55b0ac1270227c73d188582856d4d 100644
--- a/src/js/macros.py
+++ b/src/js/macros.py
@@ -60,6 +60,7 @@
 macro IS_NUMBER(arg)            = (typeof(arg) === 'number');
 macro IS_OBJECT(arg)            = (typeof(arg) === 'object');
 macro IS_PROXY(arg)             = (%_IsJSProxy(arg));
+macro IS_REGEXP(arg)            = (%_IsRegExp(arg));
 macro IS_SCRIPT(arg)            = (%_ClassOf(arg) === 'Script');
 macro IS_SET(arg)               = (%_ClassOf(arg) === 'Set');
 macro IS_SET_ITERATOR(arg)      = (%_ClassOf(arg) === 'Set Iterator');