* src/bin/autfilt.cc: Return with exit code 1 if no match found.
* src/tgbaalgos/are_isomorphic.cc,src/tgbatest/degenlskip.test
src/tgbatest/explpro2.test,src/tgbatest/explpro3.test
src/tgbatest/explpro4.test,src/tgbatest/explprod.test
src/tgbatest/neverclaimread.test, src/tgbatest/readsave.test
src/tgbatest/tripprod.test: Use exit status to check for output
emptiness instead of 'test -n'.
* src/tgbatest/isomorph.test: Simplify test.
And add the corresponding --isomorphic=FILENAME option to autfilt.
* src/tgbaalgos/are_isomorphic.cc, src/tgbaalgos/are_isomorphic.hh:
New.
* src/tgbaalgos/Makefile.am: Add it.
* src/bin/autfilt.cc: Add --isomorphic option.
* src/tgbatest/isomorph.test: Test it.
* src/tgbatest/Makefile.am: Add it.
