Use __RENAME_IF_FILE_OFFSET64 where possible.

It's not usable for cases where the off_t and off64_t functions became
available in different API levels, so it's not as big an improvement as
we'd hoped, but it cleans up several headers and should be usable for
any future additions (though recent Linux additions have _only_ supported
off64_t anyway).

Bug: N/A
Test: builds
Change-Id: I18b00f30666079d9d12d5b9c0ed916076d6c3641