Make subdir-objects the default.
Make subdir-objects the default.

Automake 1.14.1 warns that this will become the default in the future
and advises enabling this, I assume to catch conflicts. We already
use this option in the opus library.

xiph/opusfile,xiph/opusfile,SmartWalkieOrg/opusfile,youfearm3/opusfile,SmartWalkieOrg/opusfile,SmartWalkieOrg/opusfile,xiph/opusfile,youfearm3/opusfile