ltl2tgba cgi updates.

* wrap/python/cgi-bin/ltl2tgba.in (dot): Use the value computed by
configure.
(os.system): Cleanup stale files only when the form has been
submitted.
(list options): Keep track of the selected value.
(draw_acc_run|print_acc_run): set ec=0 to detect if it has been
later set or not.  Fix error message when using generalized
automata with degeneralized emptiness checks.
* wrap/python/cgi-bin/Makefile.am (ltl2tgba.py): Substitute @DOT@.

wrap/python/cgi-bin/Makefile.am

@@ -29,6 +29,7 @@ ltl2tgba.py: $(srcdir)/ltl2tgba.in Makefile
 	    -e 's|[@]srcdir[@]|@srcdir@|g' \
 	    -e 's|[@]top_builddir[@]|@top_builddir@|g' \
 	    -e 's|[@]PACKAGE_VERSION[@]|@PACKAGE_VERSION@|g' \
+	    -e 's|[@]DOT[@]|@DOT@|g' \
 	    <$(srcdir)/ltl2tgba.in >ltl2tgba.tmp
 	chmod +x ltl2tgba.tmp
 	mv -f ltl2tgba.tmp $@