pgsql: Replace insertion sort in contrib/intarray with qsort().

Replace insertion sort in contrib/intarray with qsort().

It's all very well to claim that a simplistic sort is fast in easy
cases, but O(N^2) in the worst case is not good ... especially if the
worst case is as easy to hit as "descending order input".  Replace that
bit with our standard qsort.

Per bug #12866 from Maksym Boguk.  Back-patch to all active branches.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/8d1f239003d0245dda636dfa6cf0add13bee69d6

Modified Files
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contrib/intarray/_int_tool.c |   52 +++++++++++++++++++-----------------------
1 file changed, 23 insertions(+), 29 deletions(-)