Cleanup the printf code to make it smaller and more modular.

Fix a memory leak in the new OP_ContextPush opcode. (CVS 1258)

FossilOrigin-Name: 2756f7af3382fa9d186ab99cf76f469fb891a3c3

src/vdbeaux.c

@@ -787,6 +787,8 @@ static void Cleanup(Vdbe *p){
     p->keylistStackDepth = 0;
     p->keylistStack = 0;
   }
+  sqliteFree(p->contextStack);
+  p->contextStack = 0;
   sqliteFree(p->zErrMsg);
   p->zErrMsg = 0;
 }