change blockchain -> block chain (spelling)

- Wiki says "block chain" is correct ;)
- remove some unneeded spaces I found in the source, while fixing the spelling

src/test/DoS_tests.cpp

@@ -46,7 +46,7 @@ BOOST_AUTO_TEST_CASE(DoS_banning)
     BOOST_CHECK(CNode::IsBanned(addr1));  // ... but 1 still should be
     dummyNode2.Misbehaving(50);
     BOOST_CHECK(CNode::IsBanned(addr2));
-}    
+}
 
 BOOST_AUTO_TEST_CASE(DoS_banscore)
 {
@@ -99,7 +99,7 @@ BOOST_AUTO_TEST_CASE(DoS_checknbits)
 {
     using namespace boost::assign; // for 'map_list_of()'
 
-    // Timestamps,nBits from the bitcoin blockchain.
+    // Timestamps,nBits from the bitcoin block chain.
     // These are the block-chain checkpoint blocks
     typedef std::map<int64, unsigned int> BlockData;
     BlockData chainData =
@@ -129,7 +129,6 @@ BOOST_AUTO_TEST_CASE(DoS_checknbits)
 
     // ... but OK if enough time passed for difficulty to adjust downward:
     BOOST_CHECK(CheckNBits(firstcheck.second, lastcheck.first+60*60*24*365*4, lastcheck.second, lastcheck.first));
-    
 }
 
 CTransaction RandomOrphan()