* src/tgba/tgbagraph.hh: New file.
* src/tgba/Makefile.am: Add it.
* src/graph/graph.hh: Add methods needed by tgbagraph.hh.
* src/graphtest/tgbagraph.cc, src/graphtest/tgbagraph.test: New files.
* src/graphtest/Makefile.am: Add them.