expat: use gzip-native for unpack

expat: use gzip-native for unpack

expat 2.0.1 archive is generated with DOS format, which causes CRC
error for some version of gzip (<1.4), e.g. on Unbuntu 10.04. This
commit adds do_unpack dependency to gzip-native, and thus to use
local compiled binary to address this issue. Since 1.4 is a known
version solving this issue, also specify a default version for
gzip-native

also move most lines into expat.inc as cleanup

Signed-off-by: Kevin Tian <kevin.tian@intel.com>