plot -Tver temporary

[utzoo!henry]

As distributed, the Versatec filter in plot(1) makes its scan-conversion
temporary in /usr/tmp/raster rather than using a unique name, and leaves
it around afterwards.  It creates it rw-rw-rw- so that in theory the next
user to run Versatec output simply stomps it.  Problem:  if the first user
has a non-zero umask, this doesn't work.  Worse, vplot does not complain,
and subsequent users get copies of the first user's output rather than
their own.  This is easily fixed:

	1. Change the initialization of picture to be "/tmp/verXXXXXX"
		(or maybe "/usr/tmp/verXXXXXX").
	2. Precede the creat of picture with mktemp(picture); .  You
		might also want to change the creat mode to 0600.
	3. Put an unlink(picture); before the exit() at the end of main.
	4. Put an unlink(picture); before the exit() in onintr.

The only capability this loses is the ability to replot an old raster
file without scan-converting again.  This doesn't seem a real problem.
In fact, does anybody know why such a useless capability was included
in the first place?