bin: fix destruction order of global variables
Fixes #142, reported by Joachim Klein. * bin/autfilt.cc, bin/ltlfilt.cc, bin/randaut.cc, bin/randltl.cc: Make sure all global variables that have a destructor are destructed in the main. Otherwise they risk being destructed after the library's global structures are destructed, causing access to freed memory. * NEWS: Mention the bug.