[Doc] Bump Doxyfile to pre-2.2
[Doc] Bump Doxyfile to pre-2.2

Now that 2.1.7 has been branched off, master is 2.1.99 (pre-2.2).

DMDcoin/Diamond,Mrs-X/PIVX,dev1972/Satellitecoin,dev1972/Satellitecoin,Darknet-Crypto/Darknet,PIVX-Project/PIVX,DMDcoin/Diamond,benzmuircroft/REWIRE.io,ColossusCoinXT/ColossusCoinXT,Mrs-X/PIVX,Mrs-X/Darknet,48thct2jtnf/P,Vsync-project/Vsync,CoinProjects/AmsterdamCoin-v4,npccoin/npccoin,benzmuircroft/REWIRE.io,48thct2jtnf/P,Bloom-Project/Bloom,pelorusjack/BlockDX,slingcoin/sling-market,midnight-miner/LasVegasCoin,DMDcoin/Diamond,ColossusCoinXT/ColossusCoinXT,LIMXTEC/DMDv3,Darknet-Crypto/Darknet,LIMXTEC/DMDv3,npccoin/npccoin,presstab/PIVX,keesdewit82/LasVegasCoin,CoinProjects/AmsterdamCoin-v4,Bloom-Project/Bloom,PIVX-Project/PIVX,keesdewit82/LasVegasCoin,Mrs-X/PIVX,Bloom-Project/Bloom,pelorusjack/BlockDX,Bloom-Project/Bloom,PIVX-Project/PIVX,pelorusjack/BlockDX,PIVX-Project/PIVX,ColossusCoinXT/ColossusCoinXT,slingcoin/sling-market,LIMXTEC/DMDv3,48thct2jtnf/P,DMDcoin/Diamond,Vsync-project/Vsync,midnight-miner/LasVegasCoin,Mrs-X/PIVX,CoinProjects/AmsterdamCoin-v4,LIMXTEC/DMDv3,keesdewit82/LasVegasCoin,benzmuircroft/REWIRE.io,pelorusjack/BlockDX,PIVX-Project/PIVX,Mrs-X/Darknet,PIVX-Project/PIVX,DMDcoin/Diamond,CoinProjects/AmsterdamCoin-v4,Mrs-X/PIVX,Bloom-Project/Bloom,Mrs-X/Darknet,benzmuircroft/REWIRE.io,keesdewit82/LasVegasCoin,Darknet-Crypto/Darknet,slingcoin/sling-market,dev1972/Satellitecoin,npccoin/npccoin,slingcoin/sling-market,48thct2jtnf/P,Darknet-Crypto/Darknet,Mrs-X/Darknet,LIMXTEC/DMDv3,presstab/PIVX,ColossusCoinXT/ColossusCoinXT,PIVX-Project/PIVX,dev1972/Satellitecoin,presstab/PIVX,Bloom-Project/Bloom,presstab/PIVX,pelorusjack/BlockDX,keesdewit82/LasVegasCoin,npccoin/npccoin,Darknet-Crypto/Darknet,PIVX-Project/PIVX,DMDcoin/Diamond,pelorusjack/BlockDX,Vsync-project/Vsync,npccoin/npccoin,benzmuircroft/REWIRE.io,midnight-miner/LasVegasCoin,benzmuircroft/REWIRE.io,slingcoin/sling-market,ColossusCoinXT/ColossusCoinXT,midnight-miner/LasVegasCoin,midnight-miner/LasVegasCoin,CoinProjects/AmsterdamCoin-v4,PIVX-Project/PIVX,slingcoin/sling-market,Darknet-Crypto/Darknet,presstab/PIVX,keesdewit82/LasVegasCoin,48thct2jtnf/P,Mrs-X/PIVX,npccoin/npccoin,dev1972/Satellitecoin,dev1972/Satellitecoin,Vsync-project/Vsync,CoinProjects/AmsterdamCoin-v4,Mrs-X/Darknet,Vsync-project/Vsync,LIMXTEC/DMDv3,48thct2jtnf/P,ColossusCoinXT/ColossusCoinXT,Mrs-X/Darknet,presstab/PIVX,Vsync-project/Vsync,midnight-miner/LasVegasCoin