internal miner: move 2 globals from main to miner

- moves 2 global variables from main.cpp/h to miner.cpp/h
- also removes 2 unneded includes in miner.cpp, that come from miner.h
  already

src/main.cpp

@@ -67,9 +67,6 @@ CScript COINBASE_FLAGS;
 
 const string strMessageMagic = "Bitcoin Signed Message:\n";
 
-double dHashesPerSec = 0.0;
-int64 nHPSTimerStart = 0;
-
 // Settings
 int64 nTransactionFee = 0;