Switch to xz tarball

Signed-off-by: Daniel Engberg <daniel.engberg.lists@pyret.net>

GNU M4 is a prerequisite to run autoconf and automake.

This patch packages the macro processor.

This is a prerequisite for packaging autoconf and automake.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>

[Fixed commit summary according to our best-practise]

Signed-off-by: Michael Heimpold <mhei@heimpold.de>