* bin/common_post.cc, bin/randaut.cc: Implement -b/--buchi.
Also add --sba as alias for -B, and --gba as alias for --tgba.
* NEWS: Document those changes.
* doc/org/ltl2tgba.org, doc/org/oaut.org: Adjust documentation.
* tests/core/ltl2tgba2.test, tests/core/ltlcross2.test,
tests/core/randaut.test: Add more tests.
* tests/core/sbacc.test: --sbacc cannot be abbreviated as --sba
anymore.
* bin/common_conv.cc, bin/common_conv.hh: Here.
* bin/autfilt.cc, bin/common_trans.cc, bin/ltlcross.cc, bin/ltldo.cc,
bin/ltlfilt.cc, bin/ltlgrind.cc, bin/randaut.cc, bin/randltl.cc: Pass
the name of the argumennt to the conversion function.
* tests/core/ltlcross3.test, tests/core/ltldo.test,
tests/core/randaut.test: Add test cases.
* spot/twa/acc.cc: Factor all the error reporting code in a single
place, and improve the error message at end of acceptance.
* tests/core/randaut.test: Add more tests.