In AppendedList, qualify call to KDevVarLengthArray::append with 'this'.

Fixes build error in clang:

language/duchain/appendedlist_static.h:101:9: error:

Use of undeclared identifier 'append'
  append(data[a]);

util/kdevvarlengtharray.h:171:17: note:

Must qualify identifier to find this declaration in dependent base class
  inline void append(const T &t) {