busybox

mount: support "nofail" option. Closes 8551

function                                             old     new   delta
singlemount                                         1045    1060     +15
mount_option_str                                     338     345      +7
mount_it_now                                         355     361      +6
mount_options                                        172     176      +4
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(add/remove: 0/0 grow/shrink: 4/0 up/down: 32/0)               Total: 32 bytes

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