Merged jcorgan/ptrfix -r8827:8843 into the trunk.

Merged jcorgan/ptrfix -r8827:8843 into the trunk.

Fix that allows C++ classes derived from gr_hier_block2 to
use the new self() method to get a magic object that can be passed
to connect or disconnect to refer to their own inputs and outputs.

Note that the constructor wrapper of all classes derived from
gr_hier_block2 (and thus gr_top_block too) MUST USE the new
gnuradio::get_initial_sptr function to get the initial shared pointer.
gnuradio::get_initial_sptr works on all block types, and should be
used in all new code. See qa_gr_hier_block2_derived.{h,cc} for an
example.

git-svn-id: http://gnuradio.org/svn/gnuradio/trunk@8844 221aa14e-8319-0410-a670-987f0aec2ac5