g_idle_add() is discouraged, and the checkpatch.pl script warns
about it.
Sometimes there is a legitimate use of it, when you want to always
schedule an idle action (without intent to cancel or track it). That
makes more sense for g_idle_add() than it does for g_timeout_add(),
because a timeout really should be tracked and cancelled if necessary.
Add a wrapper to rename the legitimate uses. This way, we can avoid the
checkpatch.pl warnings, and can grep for the remaining illegitimate uses.
a99ac7ccd8