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/timedata.cpp

@@ -1,5 +1,5 @@
 // Copyright (c) 2014 The Bitcoin developers
-// Distributed under the MIT/X11 software license, see the accompanying
+// Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include "timedata.h"
@@ -17,14 +17,13 @@ using namespace std;
 static CCriticalSection cs_nTimeOffset;
 static int64_t nTimeOffset = 0;
 
-//
-// "Never go to sea with two chronometers; take one or three."
-// Our three time sources are:
-//  - System clock
-//  - Median of other nodes clocks
-//  - The user (asking the user to fix the system clock if the first two disagree)
-//
-//
+/**
+ * "Never go to sea with two chronometers; take one or three."
+ * Our three time sources are:
+ *  - System clock
+ *  - Median of other nodes clocks
+ *  - The user (asking the user to fix the system clock if the first two disagree)
+ */
 int64_t GetTimeOffset()
 {
     LOCK(cs_nTimeOffset);