Fix 32 bit wrapping issue in bulkRead.
Fix 32 bit wrapping issue in bulkRead.

This should fix downloading large (> 2G) files on 32-bit platforms.

cmars/tools,FracturedRetina/go-mtpfs,riwsakiP8/riwsakiza-go-mtpfs,cmars/tools,wisavalite/go-mtpfs,cmars/tools,FracturedRetina/go-mtpfs,riwsakiP8/riwsakiza-go-mtpfs,FracturedRetina/go-mtpfs,wisavalite/go-mtpfs,riwsakiP8/riwsakiza-go-mtpfs,cmars/tools,wisavalite/go-mtpfs