Model lyx_exit() to tell coverity what it does

development/coverity_modeling.cpp

@@ -10,10 +10,17 @@ void doAssertWithCallstack(bool value)
 	}
 }
 
+
 // Tell coverity that this function always exits
 void doAppErr(char const * expr, char const * file, long line)
 {
 	__coverity_panic__();
 }
 
+
+void lyx_exit(int exit_code)
+{
+	__coverity_panic__();
+}
+
 }