Fix proposal for issue #13

It is going to be submitted as pull request, so let's see how travis-ci will handle this.

src/backends/postgresql/statement.cpp

@@ -49,7 +49,7 @@ void postgresql_statement_backend::clean_up()
         PQclear(result_);
         result_ = NULL;
 
-        if (statementName_.empty() == false)
+        if (stType_ != st_repeatable_query && statementName_.empty() == false)
         {
             session_.deallocate_prepared_statement(statementName_);
             statementName_.clear();