Add hashCode() for primitives. (#104)

backend.native/tests/runtime/basic/hash0.kt

@@ -0,0 +1,18 @@
+fun main(args : Array<String>) {
+    println(239.hashCode())
+    println((-1L).hashCode())
+    println('a'.hashCode())
+    println(1.0f.hashCode())
+    println(1.0.hashCode())
+    println(true.hashCode())
+    println(false.hashCode())
+    println(Any().hashCode() != Any().hashCode())
+    val a = CharArray(5)
+    a[0] = 'H'
+    a[1] = 'e'
+    a[2] = 'l'
+    a[3] = 'l'
+    a[4] = 'o'
+    // Note that it uses private Konan API.
+    println("Hello".hashCode() == fromCharArray(a, 0, 5).hashCode())
+}