* src/tgba/tgbagraph.hh (new_state, new_states, new_transitions, out,
trans_data): Delegate these useful graph methods so we do not have to
call get_graph().
* src/graphtest/tgbagraph.cc, src/tgbaalgos/dtbasat.cc,
src/tgbaalgos/dtgbasat.cc, src/tgbaalgos/dupexp.cc,
src/tgbaalgos/emptiness.cc, src/tgbaalgos/lbtt.cc,
src/tgbaalgos/powerset.cc, src/tgbaalgos/randomgraph.cc,
src/tgbaalgos/sccfilter.cc,
src/tgbaalgos/sccinfo.cc,src/tgbaalgos/simulation.cc: Simplify.