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/ecwrapper.cpp

@@ -13,9 +13,11 @@
 
 namespace {
 
-// Perform ECDSA key recovery (see SEC1 4.1.6) for curves over (mod p)-fields
-// recid selects which key is recovered
-// if check is non-zero, additional checks are performed
+/**
+ * Perform ECDSA key recovery (see SEC1 4.1.6) for curves over (mod p)-fields
+ * recid selects which key is recovered
+ * if check is non-zero, additional checks are performed
+ */
 int ECDSA_SIG_recover_key_GFp(EC_KEY *eckey, ECDSA_SIG *ecsig, const unsigned char *msg, int msglen, int recid, int check)
 {
     if (!eckey) return 0;