TAJO-1177: Reduce the use of Sun proprietary API. (Jihun Kang via hyunsik)

Closes #243
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into index_support
Merge branch 'index_support' of https://git-wip-us.apache.org/repos/asf/tajo into index_support