KT-2752: add checkers for inconsistent usage of JsName

js/js.translator/testData/box/nameClashes/jsNameAndPrivate.kt

@@ -0,0 +1,12 @@
+package foo
+
+@JsName("bar") fun foo(x: Int) = x
+
+private fun bar() = 42
+
+fun box(): String {
+    assertEquals(23, foo(23))
+    assertEquals(42, bar())
+
+    return "OK"
+}