* qemud/conf.[ch]: implement parsing and saving network
configs.
* qemud/driver.c: flesh out the stubs
* qemud/internal.h: add networks list etc. to
struct qemud_server
* qemud/qemud.c: add qemudStartNetworkDaemon() and
qemudShutdownNetworkDaemon() stubs.
* qemud/qemud.c: Re-factor out qemudExec() so that it can
be used to launch dnsmasq.
* qemud/conf.c: don't return argc from qemudBuildCommandLine()
as exec() doesn't need it.
* qemud/conf.c: Re-factor bits of conf.c so that:
- qemudMakeConfigPath() can be re-used given another configDir
- split qemudEnsureConfigDir() out of qemudSaveConfig() so
that it may be re-used to create another configDir
- split qemudScanConfigDir() out so that qemudScanConfigs()
can scan multiple configDirs
* qemud/conf.c: handle an unspecified MAC address,
fix the argv freeing code in qemudBuildCommandLine()
and fix copy and paste error in qemudGenerateXML()
