Prefer dist-xz to dist-bzip2. This requires automake 1.11.

Prefer dist-xz to dist-bzip2. This requires automake 1.11.

The newer xz compression utility offers superiour compression
efficiency *and* speed over bzip2. Since adoption of bzip2
never became near universal, we still provide gzip for those
on older or more conservative systems. Furthermore, for smaller
archives the performance penalty often doesn't pay for the savings
in transfer time we might as well replace the 'smaller' bzip2
option with xz, which at least does better in this regard.

Since Automake 1.11 isn't available in all environments yes
(e.g. some scratchbox toolchains) we leave the old Makefile.am
AUTOMAKE_OPTIONS line commented out. Just uncomment this to
build on systems with older automakes.

svn path=/trunk/vorbis/; revision=17614