When making a copy of the memory allocated from the default memory allocator,
make sure the new copy has the same alignment as the original memory.
See https://bugzilla.gnome.org/show_bug.cgi?id=680796
Remove the user_data from the alloc vmethod. Subclasses that implement a new
alloc function can also implement their own vmethod to pass extra arguments. We
can then also require that custom allocators implement an alloc function so that
gst_allocator_alloc() always works.
Make GstAllocator a GstObject instead of a GstMiniObject, like bufferpool.
Make a new gstallocator.c file. Make a GstAllocator subclass for the default
allocator.
