You know with D/P/PL you can "trade" to evovle pokemon with the GTS right? You put the pokemon you want to evovle up in the GTS, and ask for something like a lvl 100 legendary.
then go Search for any pokemon in the GTS and trade with someone, Once you spend the 20-30minutes looking for a trade thats reasonable and you can actually do, Complete it, and take back your Haunter, And when you do, it will evovle into a Gengar.