Add more directories under control of autotools.

I should have staged and committed these changes separately, but I am
too lazy to deal with that.

The main changes in this commit are that I added the derive macro that
automates the delegation of the Graph trait.  This saves a lot of
boiler-plate codes.

The second main change, perhaps the most important one, is that I
found and tried to fix a bug that caused duplication of nodes.  The
bug arises from splitting or cloning a node multiple times, and
immediately planting the same fragment under the new "sploned" node.
That is, when we try to splone the node again, we found that we need
to splone, because the node that was created by the same sploning
process now has a different label because of the planting of the
fragment.  Then after the sploning, we plant the fragment again.  This
makes the newly sploned node have the same label (except for the clone
index) and the same children as the node that was sploned and planted
in the previous rounds.

The fix is to check for the existence of a node that has the same set
of children as the about-to-be-sploned node, except for the last one,
which contains the about-to-be-planted fragment as a prefix.  If that
is the case, treat it as an already existing node, so that we do not
have to splone the node again.

This is consistent with the principle to not create what we do not
need.

The macro `graph_derive` can automatically write the boiler-plate
codes for wrapper types one of whose sub-fields implements the `Graph`
trait.  The generated implementation will delegate the `Graph`
operations to the sub-field which implements the `Graph` trait.

I plan to add more macros, corresponding to various other
graph-related traits, so that no such boiler-plate codes are needed,
at least for my use-cases.

I have an ostensibly working prototype now.

Further tests are needed to make sure that the algorithm meets the
time complexity requirement, though.

An attempt to write a derive macro to automatically derive the various
graph traits.