[parted-devel] make tests work also on linux-2.6.8 w/Debian-sid-based tools

[Jim Meyering]

Since Bob Proulx has been kind enough to set up a buildbot for
parted, it's the least I can do to make sure the tests pass on the
admittedly-aging system we're currently using (linux-2.6.8 w/Debian-sid).

There were three problems:

  1) libreadline-5.0 doesn't always echo its input, and caused output-mismatch
  My first cut was to make configure reject the older libreadline
  (5.2 is fine.  I don't know about 5.1).
  That didn't help because the code that's used when there is no readline
  support did the same thing (no echo).  So the second part fixes that, too.

  2) t0100-print.sh was failing.  I tracked it down to the fact that
  read and/or lseek work differently when the file is too small as in
  that example.  IMHO, finding the details of the root cause is not
  worth the trouble of digging further, since the fix is simply to
  use a slightly larger input file.

  3) t0000-basic.sh had the same sort of problem because it erased an
  earlier label with just 1KB of zeros.  Using 4KB created a large enough
  file to fix that.

I'll send two separate patches, first #1,
then #2 and #3 together.