get rid of mapPubKeys

Make CKeyStore's interface work on uint160's instead of pubkeys, so
no separate global mapPubKeys is necessary anymore.

src/main.cpp

@@ -21,9 +21,6 @@ set<CWallet*> setpwalletRegistered;
 
 CCriticalSection cs_main;
 
-CCriticalSection cs_mapPubKeys;
-map<uint160, vector<unsigned char> > mapPubKeys;
-
 map<uint256, CTransaction> mapTransactions;
 CCriticalSection cs_mapTransactions;
 unsigned int nTransactionsUpdated = 0;