add collations and constants from MySQL 5.7.10

Author: tmtm

ext/mysql/ext.c

@@ -250,6 +250,10 @@ enum {
     TYPE_NEWDATE     = 14,
     TYPE_VARCHAR     = 15,
     TYPE_BIT         = 16,
+    TYPE_TIMESTAMP2  = 17,
+    TYPE_DATETIME2   = 18,
+    TYPE_TIME2       = 19,
+    TYPE_JSON        = 245,
     TYPE_NEWDECIMAL  = 246,
     TYPE_ENUM        = 247,
     TYPE_SET         = 248,