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/timedata.h

@@ -73,4 +73,4 @@ int64_t GetTimeOffset();
 int64_t GetAdjustedTime();
 void AddTimeData(const CNetAddr& ip, int64_t nTime);
 
-#endif
+#endif // BITCOIN_TIMEDATA_H