dumpdir bug

[utzoo!decvax!watmath!dmmartindale]

Dumpdir has exactly the same bug that Dennis Ritchie found in restor.
The fix is the same, applied in the same place.
Dennis's original bug report was:

	The restor program as distributed in V7, 32V, and 4.xBSD (at least)
	has a subscript bug that appears if you do "restor x" and there are
	too many directories on the tape.  "Too many" is 2000 for V7 and
	3000 for BSD.   The effect on the PDP-11 is that you begin to get
	nothing but checksum errors while reading the tape.

	To fix it, look a few lines after the label 'finish:'.
	Put in a test to make sure  ipos  does not get >= MAXINO.

			Dennis Ritchie

By the way, I needed to grow MAXINO to 4000 to accomodate one of my
filesystems.