Add deprecated message to NullTime (#1144)

* Add deprecated message to NullTime
* remove NullTime from README

Author: shogo82148

README.md

@@ -459,8 +459,6 @@ However, many want to scan MySQL `DATE` and `DATETIME` values into `time.Time` v
 
 **Caution:** As of Go 1.1, this makes `time.Time` the only variable type you can scan `DATE` and `DATETIME` values into. This breaks for example [`sql.RawBytes` support](https://github.com/go-sql-driver/mysql/wiki/Examples#rawbytes).
 
-Alternatively you can use the [`NullTime`](https://godoc.org/github.com/go-sql-driver/mysql#NullTime) type as the scan destination, which works with both `time.Time` and `string` / `[]byte`.
-
 
 ### Unicode support
 Since version 1.5 Go-MySQL-Driver automatically uses the collation ` utf8mb4_general_ci` by default.

nulltime_go113.go

@@ -28,4 +28,8 @@ import (
 //  }
 //
 // This NullTime implementation is not driver-specific
+//
+// Deprecated: NullTime doesn't honor the loc DSN parameter.
+// NullTime.Scan interprets a time as UTC, not the loc DSN parameter.
+// Use sql.NullTime instead.
 type NullTime sql.NullTime