Revert merge of pull #4845

It breaks the new mingw tests!

See

- https://travis-ci.org/bitcoin/bitcoin/jobs/36845581
- https://travis-ci.org/bitcoin/bitcoin/jobs/36845582

This reverts commit 4705902777, 5e2e7fcb99, a25fd6be13.

src/chainparamsbase.cpp

@@ -57,20 +57,6 @@ public:
 };
 static CBaseRegTestParams regTestParams;
 
-//
-// Unit test
-//
-class CBaseUnitTestParams : public CBaseMainParams
-{
-public:
-    CBaseUnitTestParams()
-    {
-        networkID = CBaseChainParams::UNITTEST;
-        strDataDir = "unittest";
-    }
-};
-static CBaseUnitTestParams unitTestParams;
-
 static CBaseChainParams* pCurrentBaseParams = 0;
 
 const CBaseChainParams& BaseParams()
@@ -91,9 +77,6 @@ void SelectBaseParams(CBaseChainParams::Network network)
     case CBaseChainParams::REGTEST:
         pCurrentBaseParams = &regTestParams;
         break;
-    case CBaseChainParams::UNITTEST:
-        pCurrentBaseParams = &unitTestParams;
-        break;
     default:
         assert(false && "Unimplemented network");
         return;