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.
* src/qemu/qemu_command.c (qemuBuildChrChardevStr): Alter the
chardev alias.
(qemuBuildCommandLine): Output an id for the chardev counterpart.
* tests/qemuxml2argvdata/*: Update tests to match.
Reported by Daniel P. Berrange.
