Convert remaining comments in /src to doxygen format

- Update comments in checkpoints to be doxygen compatible
- Update comments in checkqueue to be doxygen compatible
- Update coins to be doxygen compatible
- Fix comment typo in crypter.h
- Update licenses/copyright dates

Closes #5325 #5184 #5183 #5182

src/checkpoints.h

@@ -1,5 +1,5 @@
-// Copyright (c) 2009-2013 The Bitcoin developers
-// Distributed under the MIT/X11 software license, see the accompanying
+// Copyright (c) 2009-2014 The Bitcoin developers
+// Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #ifndef BITCOIN_CHECKPOINTS_H
@@ -11,7 +11,8 @@
 
 class CBlockIndex;
 
-/** Block-chain checkpoints are compiled-in sanity checks.
+/** 
+ * Block-chain checkpoints are compiled-in sanity checks.
  * They are updated every release or three.
  */
 namespace Checkpoints
@@ -25,13 +26,13 @@ struct CCheckpointData {
     double fTransactionsPerDay;
 };
 
-// Returns true if block passes checkpoint checks
+//! Returns true if block passes checkpoint checks
 bool CheckBlock(int nHeight, const uint256& hash);
 
-// Return conservative estimate of total number of blocks, 0 if unknown
+//! Return conservative estimate of total number of blocks, 0 if unknown
 int GetTotalBlocksEstimate();
 
-// Returns last CBlockIndex* in mapBlockIndex that is a checkpoint
+//! Returns last CBlockIndex* in mapBlockIndex that is a checkpoint
 CBlockIndex* GetLastCheckpoint();
 
 double GuessVerificationProgress(CBlockIndex* pindex, bool fSigchecks = true);