bin: add support for SPOT_DEFAULT_FORMAT

* bin/common_aoutput.cc, bin/common_aoutput.hh, bin/common_setup.cc:
Implement it.
* NEWS, bin/man/spot-x.x: Document it.
* tests/core/readsave.test: Test it.

bin/common_setup.cc

@@ -18,6 +18,8 @@
 // along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 #include "common_setup.hh"
+#include "common_aoutput.hh"
+
 #include "argp.h"
 #include <cstdlib>
 #include <iostream>
@@ -40,6 +42,7 @@ This is free software: you are free to change and redistribute it.\n\
 There is NO WARRANTY, to the extent permitted by law.\n", stream);
 }
 
+
 #ifdef HAVE_SIGACTION
 static void sig_handler(int sig)
 {
@@ -81,6 +84,7 @@ setup(char** argv)
 
   std::ios_base::sync_with_stdio(false);
 
+  setup_default_output_format();
   setup_sig_handler();
 }