Rename interestingArgv to explicitArgv.

Summary: interestingArgv isn't a very useful name, see D9607#45.

Test Plan: N/A

Reviewers: epriestley, Blessed Reviewers

Reviewed By: epriestley, Blessed Reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9617