Don't forcibly instantiate abstract classes

If a class is abstract then there definitely isn't an instance of it so
we shouldn't load those methods.

Author: thk123

jbmc/src/java_bytecode/ci_lazy_methods_needed.cpp

@@ -51,9 +51,13 @@ bool ci_lazy_methods_neededt::add_needed_class(
 void ci_lazy_methods_neededt::add_all_needed_classes(const pointer_typet &pointer_type)
 {
   namespacet ns{symbol_table};
-  initialize_instantiated_classes_from_pointer(
-    pointer_type,
-    ns);
+  const java_class_typet &underlying_type =
+    to_java_class_type(ns.follow(pointer_type.subtype()));
+
+  if(underlying_type.is_abstract())
+    return;
+
+  initialize_instantiated_classes_from_pointer(pointer_type, ns);
 
   // TODO we should be passing here a map that maps generic parameters
   // to concrete types in the current context TG-2664