busybox

losetup: implement -r option. Closes 4033.

function                                             old     new   delta
packed_usage                                       28595   28633     +38
losetup_main                                         285     290      +5
singlemount                                          906     908      +2
set_loop                                             674     672      -2

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>