[JS IR] stdlib: Fix bugs in Long.toString(radix)

libraries/stdlib/js-ir/src/kotlin/text/numberConversions.kt

@@ -0,0 +1,15 @@
+/*
+ * Copyright 2010-2019 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package kotlin.text
+
+/**
+ * Returns a string representation of this [Long] value in the specified [radix].
+ *
+ * @throws IllegalArgumentException when [radix] is not a valid radix for number to string conversion.
+ */
+@SinceKotlin("1.2")
+public actual fun Long.toString(radix: Int): String =
+    this.toStringImpl(checkRadix(radix))