for the same reasons as in slclose().
Free the cblock in the canonical queue in pppclose(). This is a no-op in
the usual cases where the tty is being closed or the line discipline is
being switched back to the standard discipline, but it saves a cblock if
the line discipline is being switched to one that doesn't use the canonical
queue.
Add prototypes. I use `extern' in prototypes for functions with bogus
linkage. This should be fixed someday.
Continue cleaning up new init stuff yet again.