Core/Mysql: Multiple changes

- added support for setting NULL column values to MySQL wrapper in core
- replaced nonstandard strdup function and manual memory management with std::string
- fixed bug in MySQLPreparedStatement::getQueryString method, it failed when string parameter contained embedded '?' symbols
- fixed memory leak in MySQLPreparedStatement::setString method

1 files changed, 4 insertions, 1 deletions

diff --git a/src/server/shared/Database/Transaction.h b/src/server/shared/Database/Transaction.h
index 9b7f9afc30b..026cc1fdf96 100644
--- a/src/server/shared/Database/Transaction.h
+++ b/src/server/shared/Database/Transaction.h
@@ -29,6 +29,9 @@ class Transaction
     friend class TransactionTask;
     friend class MySQLConnection;
 
+    template <typename T>
+    friend class DatabaseWorkerPool;
+
     public:
         Transaction() : _cleanedUp(false) {}
         ~Transaction() { Cleanup(); }
@@ -65,4 +68,4 @@ class TransactionTask : public SQLOperation
         SQLTransaction m_trans;
 };
 
-#endif
\ No newline at end of file
+#endif