Fixed memory leaks etc

tests/ident.c

@@ -31,6 +31,7 @@ bool suite_ident(void) {
   mpc_test(Ident, "", "", string_eq, free, string_print);
   mpc_test(Ident, "18nums", "", string_eq, free, string_print);
   
+  mpc_undefine(Ident);
   mpc_delete(Ident);
   
   return true;

tests/math.c

@@ -46,6 +46,11 @@ bool suite_math(void) {
   mpc_test(Maths, "a", (int[]){ 0 }, int_eq, free, int_print);
   mpc_test(Maths, "2b+4", (int[]){ 2 }, int_eq, free, int_print);
   
+  mpc_undefine(Expr);
+  mpc_undefine(Factor);
+  mpc_undefine(Term);
+  mpc_undefine(Maths);
+  
   mpc_delete(Expr);
   mpc_delete(Factor);
   mpc_delete(Term);