Add rows_columntypes.go from upstream mysql driver patch

This is a temporary move until the columntype branch lands
upstream.

Implementation here:
go-sql-driver#495

Author: Peter Teichman

rows_columntypes.go

@@ -0,0 +1,78 @@
+package mysql
+
+const (
+	// In case we get something unexpected
+	FieldTypeUnknown = "UNKNOWN"
+
+	// Human-readable names for each distinct type byte
+	FieldTypeNameDecimal    = "DECIMAL"
+	FieldTypeNameTiny       = "TINY"
+	FieldTypeNameShort      = "SHORT"
+	FieldTypeNameLong       = "LONG"
+	FieldTypeNameFloat      = "FLOAT"
+	FieldTypeNameDouble     = "DOUBLE"
+	FieldTypeNameNULL       = "NULL"
+	FieldTypeNameTimestamp  = "TIMESTAMP"
+	FieldTypeNameLongLong   = "LONGLONG"
+	FieldTypeNameInt24      = "INT24"
+	FieldTypeNameDate       = "DATE"
+	FieldTypeNameTime       = "TIME"
+	FieldTypeNameDateTime   = "DATETIME"
+	FieldTypeNameYear       = "YEAR"
+	FieldTypeNameNewDate    = "NEWDATE"
+	FieldTypeNameVarChar    = "VARCHAR"
+	FieldTypeNameBit        = "BIT"
+	FieldTypeNameJSON       = "JSON"
+	FieldTypeNameNewDecimal = "NEWDECIMAL"
+	FieldTypeNameEnum       = "ENUM"
+	FieldTypeNameSet        = "SET"
+	FieldTypeNameTinyBLOB   = "TINYBLOB"
+	FieldTypeNameMediumBLOB = "MEDIUMBLOB"
+	FieldTypeNameLongBLOB   = "LONGBLOB"
+	FieldTypeNameBLOB       = "BLOB"
+	FieldTypeNameVarString  = "VARSTRING"
+	FieldTypeNameString     = "STRING"
+	FieldTypeNameGeometry   = "GEOMETRY"
+)
+
+// mapping from each type identifier to human readable string
+var mysqlTypeMap = map[byte]string{
+	fieldTypeDecimal:    FieldTypeNameDecimal,
+	fieldTypeTiny:       FieldTypeNameTiny,
+	fieldTypeShort:      FieldTypeNameShort,
+	fieldTypeLong:       FieldTypeNameLong,
+	fieldTypeFloat:      FieldTypeNameFloat,
+	fieldTypeDouble:     FieldTypeNameDouble,
+	fieldTypeNULL:       FieldTypeNameNULL,
+	fieldTypeTimestamp:  FieldTypeNameTimestamp,
+	fieldTypeLongLong:   FieldTypeNameLongLong,
+	fieldTypeInt24:      FieldTypeNameInt24,
+	fieldTypeDate:       FieldTypeNameDate,
+	fieldTypeTime:       FieldTypeNameTime,
+	fieldTypeDateTime:   FieldTypeNameDateTime,
+	fieldTypeYear:       FieldTypeNameYear,
+	fieldTypeNewDate:    FieldTypeNameNewDate,
+	fieldTypeVarChar:    FieldTypeNameVarChar,
+	fieldTypeBit:        FieldTypeNameBit,
+	fieldTypeJSON:       FieldTypeNameJSON,
+	fieldTypeNewDecimal: FieldTypeNameNewDecimal,
+	fieldTypeEnum:       FieldTypeNameEnum,
+	fieldTypeSet:        FieldTypeNameSet,
+	fieldTypeTinyBLOB:   FieldTypeNameTinyBLOB,
+	fieldTypeMediumBLOB: FieldTypeNameMediumBLOB,
+	fieldTypeLongBLOB:   FieldTypeNameLongBLOB,
+	fieldTypeBLOB:       FieldTypeNameBLOB,
+	fieldTypeVarString:  FieldTypeNameVarString,
+	fieldTypeString:     FieldTypeNameString,
+	fieldTypeGeometry:   FieldTypeNameGeometry,
+}
+
+// Make Rows implement the optional RowsColumnTypeDatabaseTypeName interface.
+// See https://github.com/golang/go/commit/2a85578b0ecd424e95b29d810b7a414a299fd6a7
+// - (go 1.8 required for this to have any effect)
+func (rows *mysqlRows) ColumnTypeDatabaseTypeName(index int) string {
+	if typeName, ok := mysqlTypeMap[rows.columns[index].fieldType]; ok {
+		return typeName
+	}
+	return FieldTypeUnknown
+}