New structure Table Value Constructor added in grammar.

TVC can be used in UNION-statement, in view and in subquery.

Files where TVC is defined and its methods are stored added.
Methods exec and prepare for TVC added.
Tests for TVC added.

sql/sql_tvc.h

@@ -0,0 +1,27 @@
+#ifndef SQL_TVC_INCLUDED
+#define SQL_TVC_INCLUDED
+#include "sql_type.h"
+#include "item.h"
+
+typedef List<Item> List_item;
+class select_result;
+
+/**
+  @class table_value_constr
+  @brief Definition of a Table Value Construction(TVC)
+	
+  It contains a list of lists of values that this TVC contains.
+*/
+
+class table_value_constr : public Sql_alloc
+{
+public:
+  List<List_item> lists_of_values;
+  select_result *result;
+  
+  bool prepare(THD *thd_arg, SELECT_LEX *sl, 
+	       select_result *tmp_result);
+  bool exec();
+};
+
+#endif /* SQL_TVC_INCLUDED */