Split yet more runtime functions into separate files.

src/runtime/runtime-regexp.cc

Index: src/runtime/runtime-regexp.cc
diff --git a/src/runtime/runtime-regexp.cc b/src/runtime/runtime-regexp.cc
index e96d50195a80aaa8233ed3da9b89282bfd0aa469..840264fc517f69967fea4e1b6c70ccd02ec71041 100644
--- a/src/runtime/runtime-regexp.cc
+++ b/src/runtime/runtime-regexp.cc
@@ -1088,6 +1088,14 @@ RUNTIME_FUNCTION(RuntimeReference_RegExpExec) {
 }
 
 
+RUNTIME_FUNCTION(RuntimeReference_IsRegExp) {
+  SealHandleScope shs(isolate);
+  DCHECK(args.length() == 1);
+  CONVERT_ARG_CHECKED(Object, obj, 0);
+  return isolate->heap()->ToBoolean(obj->IsJSRegExp());
+}
+
+
 // Perform string match of pattern on subject, starting at start index.
 // Caller must ensure that 0 <= start_index <= sub->length(),
 // and should check that pat->length() + start_index <= sub->length().