add missing header end comments

- ensures a consistent usage in header files
- also add a blank line after the copyright header where missing
- also remove orphan new-lines at the end of some files

src/chainparams.h

@@ -120,4 +120,4 @@ void SelectParams(CBaseChainParams::Network network);
  */
 bool SelectParamsFromCommandLine();
 
-#endif
+#endif // BITCOIN_CHAIN_PARAMS_H