This patch teaches testutil how to read multi-line input files with
backspace-newline line continuation markers.
The patch also breaks up all the single-line arguments test input files into
multi-line files with lines shorter than 80 characters.
* tests/testutilsqemu.c: make 'pc' an alias for qemu-system-x86_64
* tests/qemuxml2argvdata/qemuxml2argv-machine-aliases1.*,
tests/qemuxml2argvtest.c: add a test which uses qemu-system-x86_64
and make sure the machine type is canonicalized.
