busybox

zcat: if seamless uncompressors are defined, autodetect file's format

function                                             old     new   delta
bbunpack                                             526     622     +96
packed_usage                                       29335   29341      +6
gunzip_main                                           64      67      +3

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