Introduce binary representation for annotations

Will be used where annotations can't be stored elsewhere: for example,
built-ins, JS, type annotations on JDK<8

compiler/testData/serialization/annotationTargets.kt

@@ -0,0 +1,37 @@
+package test
+
+annotation class anno(val x: String)
+
+
+anno("top level function")
+fun f1(anno("top level function parameter") p: Int) {}
+
+anno("top level property")
+val p1 = null
+
+anno("extension function")
+fun Long.f2(anno("extension function parameter") p: Int) {}
+
+anno("extension property")
+val Double.p2: Double get() = null
+
+anno("top level class")
+class C1 [anno("constructor")] () {
+    anno("member function")
+    fun f3(anno("member function parameter") p: Int) {}
+
+    anno("member property")
+    val p3 = null
+
+    anno("member extension function")
+    fun String.f4() {}
+
+    anno("member extension property")
+    val Int.v4: Int get() = this
+
+    anno("nested class")
+    class C2
+
+    anno("class object")
+    class object {}
+}