MCOL-641 Replaced IDB_Decima.__v union with int128_t attribute.

Moved all tests into ./test

Introduced ./datatypes directory

tests/arithmeticoperator-tests.cpp

@@ -0,0 +1,27 @@
+/* Copyright (C) 2020 MariaDB Corporation
+
+   This program is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public License
+   as published by the Free Software Foundation; version 2 of
+   the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+   MA 02110-1301, USA. */
+
+#include <gtest/gtest.h> // googletest header file
+
+using int128_t = __int128;
+using uint128_t = unsigned __int128;
+//using CSCDataType = execplan::CalpontSystemCatalog::ColDataType;
+
+TEST(SimpleCheck, check1)
+{
+    EXPECT_EQ(true, true);
+}