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/init.cpp

@@ -639,7 +639,7 @@ bool AppInit2()
     BOOST_FOREACH(string strDest, mapMultiArgs["-seednode"])
         AddOneShot(strDest);
 
-    // ********************************************************* Step 7: load blockchain
+    // ********************************************************* Step 7: load block chain
 
     if (!bitdb.Open(GetDataDir()))
     {

src/main.cpp

@@ -1356,7 +1356,7 @@ bool CTransaction::CheckInputs(CCoinsViewCache &inputs, enum CheckSig_mode csmod
         // Helps prevent CPU exhaustion attacks.
 
         // Skip ECDSA signature verification when connecting blocks
-        // before the last blockchain checkpoint. This is safe because block merkle hashes are
+        // before the last block chain checkpoint. This is safe because block merkle hashes are
         // still computed and checked, and any change will be caught at the next checkpoint.
         if (csmode == CS_ALWAYS ||
             (csmode == CS_AFTER_CHECKPOINT && inputs.GetBestBlock()->nHeight >= Checkpoints::GetTotalBlocksEstimate())) {
@@ -1620,7 +1620,7 @@ bool CBlock::ConnectBlock(CBlockIndex* pindex, CCoinsViewCache &view, bool fJust
             return error("ConnectBlock() : WriteBlockIndex failed");
     }
 
-    // add this block to the view's blockchain
+    // add this block to the view's block chain
     if (!view.SetBestBlock(pindex))
         return false;
 

src/main.h

@@ -777,7 +777,7 @@ public:
     // unspent transaction outputs; spent outputs are .IsNull(); spent outputs at the end of the array are dropped
     std::vector<CTxOut> vout;
 
-    // at which height this transaction was included in the active blockchain
+    // at which height this transaction was included in the active block chain
     int nHeight;
 
     // version of the CTransaction; accesses to this value should probably check for nHeight as well,

src/rpcrawtransaction.cpp

@@ -299,7 +299,7 @@ Value signrawtransaction(const Array& params, bool fHelp)
             "signrawtransaction <hex string> [{\"txid\":txid,\"vout\":n,\"scriptPubKey\":hex},...] [<privatekey1>,...] [sighashtype=\"ALL\"]\n"
             "Sign inputs for raw transaction (serialized, hex-encoded).\n"
             "Second optional argument (may be null) is an array of previous transaction outputs that\n"
-            "this transaction depends on but may not yet be in the blockchain.\n"
+            "this transaction depends on but may not yet be in the block chain.\n"
             "Third optional argument (may be null) is an array of base58-encoded private\n"
             "keys that, if given, will be the only keys used to sign the transaction.\n"
             "Fourth optional argument is a string that is one of six values; ALL, NONE, SINGLE or\n"

src/test/DoS_tests.cpp

@@ -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()

src/test/script_tests.cpp

@@ -206,7 +206,7 @@ sign_multisig(CScript scriptPubKey, std::vector<CKey> keys, CTransaction transac
     // NOTE: CHECKMULTISIG has an unfortunate bug; it requires
     // one extra item on the stack, before the signatures.
     // Putting OP_0 on the stack is the workaround;
-    // fixing the bug would mean splitting the blockchain (old
+    // fixing the bug would mean splitting the block chain (old
     // clients would not accept new CHECKMULTISIG transactions,
     // and vice-versa)
     //