Add support for MySql delete from join table

Author: mythz

src/ServiceStack.OrmLite.MySql/MySqlExpression.cs

@@ -17,5 +17,12 @@ protected override string ToCast(string quotedColName)
         {
             return $"cast({quotedColName} as char(1000))";
         }
+
+        public override string ToDeleteRowStatement()
+        {
+            return base.tableDefs.Count > 1
+                ? $"DELETE {DialectProvider.GetQuotedTableName(modelDef)} {FromExpression} {WhereExpression}"
+                : base.ToDeleteRowStatement();
+        }
     }
 }

tests/ServiceStack.OrmLite.Tests/Expression/SqlExpressionDeleteTests.cs

@@ -15,8 +15,6 @@ public class SqlExpressionDeleteTests : OrmLiteTestBase
         [Test]
         public void Can_delete_entity_with_join_expression()
         {
-            if (Dialect == Dialect.MySql) return; //Not Supported
-
             using (var db = OpenDbConnection())
             {
                 db.DropAndCreateTable<Person>();