Add an info string symbol for bad states in btor backend

backends/btor/btor.cc

diff --git a/backends/btor/btor.cc b/backends/btor/btor.cc
index 9e316a0..2babd45 100644
--- a/backends/btor/btor.cc
+++ b/backends/btor/btor.cc
@@ -1070,7 +1070,16 @@
 					bad_properties.push_back(nid_en_and_not_a);
 				} else {
 					int nid = next_nid++;
-					btorf("%d bad %d\n", nid, nid_en_and_not_a);
+
+					string infostr =
+						cell->attributes.count("\\src")
+						? cell->attributes.at("\\src")
+						.decode_string()
+						.c_str()
+						: log_id(cell);
+
+					std::replace(infostr.begin(), infostr.end(), ' ', '_');
+					btorf("%d bad %d %s\n", nid, nid_en_and_not_a, infostr.c_str());
 				}
 
 				btorf_pop(log_id(cell));