stage3-armv7a_hardfp-20130209.tar.bz2, 149189948 bytes long,
md5sum b29ce23312e14eb15a143377d4a38473, was failing to unpack.
It so happened that this file has a run which exactly fills
the 90k buffer. The check was "size >= bufsize", apparently
it has to be ">".
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>