Adding `releasenotes` label for Apache ORC 1.7.0

[Dongjoon Hyun]

Hi, All.

Please add a label, `releasenotes`, to the notable JIRA issues which you want 
to add to the Apache ORC  1.7.0 release notes. This will be the first step 
toward Apache ORC 1.7.0 release.

Bests,
Dongjoon.