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/utiltime.h

@@ -17,4 +17,4 @@ void MilliSleep(int64_t n);
 
 std::string DateTimeStrFormat(const char* pszFormat, int64_t nTime);
 
-#endif
+#endif // BITCOIN_UTILTIME_H