SI-8960 Bring back the SerialVersionUID to anonymous function classes

In PR scala#1673 / 4267444, the annotation `SerialVersionId` was changed
from a `StaticAnnotation` to `ClassFileAnnotation` in order to enforce
annotation arguments to be constants. That was 2.11.0.

The ID value in the AnnotationInfo moved from `args` to `assocs`, but
the backend was not adjusted. This was fixed in PR scala#3711 / ecbc9d0 for
2.11.1.

Unfortunately, the synthetic AnnotationInfo that is added to anonymous
function classes still used the old constructor (`args` instead of
`assocs`), so extracting the value failed, and no field was added to
the classfile.

Author: lrytz

src/reflect/scala/reflect/internal/Definitions.scala

@@ -1118,7 +1118,7 @@ trait Definitions extends api.StandardDefinitions {
     lazy val ScalaInlineClass           = requiredClass[scala.inline]
     lazy val ScalaNoInlineClass         = requiredClass[scala.noinline]
     lazy val SerialVersionUIDAttr       = requiredClass[scala.SerialVersionUID]
-    lazy val SerialVersionUIDAnnotation = AnnotationInfo(SerialVersionUIDAttr.tpe, List(Literal(Constant(0))), List())
+    lazy val SerialVersionUIDAnnotation = AnnotationInfo(SerialVersionUIDAttr.tpe, List(), List(nme.value -> LiteralAnnotArg(Constant(0))))
     lazy val SpecializedClass           = requiredClass[scala.specialized]
     lazy val ThrowsClass                = requiredClass[scala.throws[_]]
     lazy val TransientAttr              = requiredClass[scala.transient]

test/files/run/t8960.scala

@@ -0,0 +1,8 @@
+object Test extends App {
+  val f = (new C).f
+  assert(f.getClass.getDeclaredFields.exists(_.getName == "serialVersionUID"))
+}
+
+class C {
+  def f = () => ()
+}