Minor documentation fix.
Minor documentation fix.

Clarify that the value returned by op_current_link() is strictly
 less than the value returned by op_link_count() for seekable
 sources.

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