JVM: Fix unsigned literals in API version < 1.5

compiler/testData/codegen/box/unsignedTypes/unsignedLiteralsInApiVersion14.kt

@@ -0,0 +1,12 @@
+// !API_VERSION: 1.4
+// KJS_WITH_FULL_RUNTIME
+// WITH_RUNTIME
+
+val x = 0u
+val y = 0uL
+
+fun box(): String {
+    if (x != 0u)  return "Fail 1"
+    if (y != 0uL) return "Fail 2"
+    return "OK"
+}