fix string errors

Author: MjnMixael

code/mission/missionparse.cpp

@@ -4972,7 +4972,7 @@ void parse_prop(mission* /*pm*/)
 		}
 
 		if (Fred_running) {
-			Warning(LOCATION, text.c_str());
+			Warning(LOCATION, "%s", text.c_str());
 		} else {
 			mprintf(("MISSIONS: %s", text.c_str()));
 		}

fred2/missionsave.cpp

@@ -5269,7 +5269,7 @@ int CFred_mission_save::save_props()
 
 				required_string_fred("$Class:");
 				parse_comments(2);
-				fout(" %s", Prop_info[p->prop_info_index].name);
+				fout(" %s", Prop_info[p->prop_info_index].name.c_str());
 
 				required_string_fred("$Location:");
 				parse_comments();

qtfred/src/mission/missionsave.cpp

@@ -5451,7 +5451,7 @@ int CFred_mission_save::save_props()
 
 				required_string_fred("$Class:");
 				parse_comments(2);
-				fout(" %s", Prop_info[p->prop_info_index].name);
+				fout(" %s", Prop_info[p->prop_info_index].name.c_str());
 
 				required_string_fred("$Location:");
 				parse_comments();