Move JSCHelpers.h and Value.h into separate package

Reviewed By: javache

Differential Revision: D3950748

fbshipit-source-id: 6315ea07f3217b485aeb4374b5f6e36333957848

ReactCommon/cxxreact/JSCUtils.cpp

@@ -0,0 +1,17 @@
+// Copyright 2004-present Facebook. All Rights Reserved.
+
+#include "JSCUtils.h"
+
+namespace facebook {
+namespace react {
+
+String jsStringFromBigString(const JSBigString& bigstr) {
+  if (bigstr.isAscii()) {
+    return String::createExpectingAscii(bigstr.c_str(), bigstr.size());
+  } else {
+    return String(bigstr.c_str());
+  }
+}
+
+}
+}