targets/audio: Move automake conversion function to prepare file.

No modification in the code.
prepare: convert_automake: Slight improvements.

xorg-dummy uses some more complex syntax: implement.
xiat: Arbitrary resolution through patched xorg-dummy.
tests/37-xiwi: Very basic xiwi test

This test is incomplete, as it is not able to connect to the
extension, so xinit parameter is never run. However, this tests
target installation, and verifies that there is no critical X
failures (e.g. X server cannot start).
xiwi: Fetch .gz archives instead of bz2

Debian does not install bzip2 by default.