More fixes that make autotools working for the empty repo

- Add a dummy lemon/list_graph.h file and put it in the Makefile.am
- Remove the unnecesary icons from doc/icons/geom folder.
- Update .hgignore

EXTRA_DIST += \

        benchmark/Makefile

if WANT_BENCHMARK

noinst_HEADERS +=

noinst_PROGRAMS +=

endif WANT_BENCHMARK