GPT: don't misbehave with e.g., a 9-entry partition

[Jim Meyering]

Just over a year ago, Robert Herndon reported that parted
would fail to read partition tables with say, 9 partition array
entries instead of the usual 128:

    http://thread.gmane.org/gmane.comp.gnu.parted.bugs/10173/

His proposed solution used in 1/4 turned out to be the best way
I could see to solve the problem.  If someone sees a cleaner
approach, please let me know.  Part of the hold up was that
I wanted a way to create an offending partition table to be
used in a test to exercise this fix.  I completed the script
in 3/4 and used it in 4/4 to ensure at least that
"parted -s $dev print" can now deal with such partition tables.

  [PATCH 1/4] gpt: prepare for tables with n_partition_array_entries
  [PATCH 2/4] gpt: don't misbehave with e.g., a 9-entry partition
  [PATCH 3/4] tests: rewrite/complete GPT-munging perl script
  [PATCH 4/4] tests: exercise the "GPT vs other-sized partition entry

Sorry it's taken so long.