Globals: Remove a bunch of Params() calls from main.cpp:

1) Chainparams: Explicit CChainParams arg for main:

-AcceptBlock
-AcceptBlockHeader
-ActivateBestChain
-ConnectTip
-InitBlockIndex
-LoadExternalBlockFile
-VerifyDB parametric constructor

2) Also pickup more Params()\. in main.cpp

3) Pass nPruneAfterHeight explicitly to new FindFilesToPrune() in main.cpp

src/test/test_bitcoin.cpp

@@ -50,6 +50,7 @@ BasicTestingSetup::~BasicTestingSetup()
 
 TestingSetup::TestingSetup(const std::string& chainName) : BasicTestingSetup(chainName)
 {
+    const CChainParams& chainparams = Params();
 #ifdef ENABLE_WALLET
         bitdb.MakeMock();
 #endif
@@ -60,7 +61,7 @@ TestingSetup::TestingSetup(const std::string& chainName) : BasicTestingSetup(cha
         pblocktree = new CBlockTreeDB(1 << 20, true);
         pcoinsdbview = new CCoinsViewDB(1 << 23, true);
         pcoinsTip = new CCoinsViewCache(pcoinsdbview);
-        InitBlockIndex();
+        InitBlockIndex(chainparams);
 #ifdef ENABLE_WALLET
         bool fFirstRun;
         pwalletMain = new CWallet("wallet.dat");