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.
The xml watchdog dump option is converted to qemu watchdog pause arg
but it is not reasonable to convert it back from qemu watchdog pause
arg since there already is a xml watchdog pause option, so a test for
the dump option to convert it from arg to xml is not added.
