[Telepathy] merge: telepathy-gabble

[Merge Monkey]

Merge to:

  telepathy-gabble

Changes:

  Simon McVittie <simon.mcvittie at collabora.co.uk>
    Document TpHeap

  Simon McVittie <simon.mcvittie at collabora.co.uk>
    In test-heap, pass NULL destructor to tp_heap_new

  Simon McVittie <simon.mcvittie at collabora.co.uk>
    Add destructor to heap.h too

  Simon McVittie <simon.mcvittie at collabora.co.uk>
    TpHeap: add destructor, used when we destroy or clear the heap - this breaks API, but hopefully no released versions of CMs are using it (tp-sofiasip doesn't)