Log Message:
Use .tar.gz instead of .tar.xz for DISTFILES.

Using .tar.xz intorduce dependency on archivers/xz,
and it require GCC_REQD=3.4, then maybe result in unwanted
dependency on lang/gcc34.
Especially on Ineterix, it has gcc-3.3, and lang/gcc34 is marked as
"not for Interix", then no chance to install packages using autoconf.

approved by wiz@.