pgsql: Add sort support routine for the inet data type.

Add sort support routine for the inet data type.

Add sort support for inet, including support for abbreviated keys.
Testing has shown that this reduces the time taken to sort medium to
large inet/cidr inputs by ~50-60% in realistic cases.

Author: Brandur Leach
Reviewed-By: Peter Geoghegan, Edmund Horner
Discussion: https://postgr.es/m/CABR_9B-PQ8o2MZNJ88wo6r-NxW2EFG70M96Wmcgf99G6HUQ3sw@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/71dcd7438664d81235c72337cbbbfa780f7a0630

Modified Files
--------------
src/backend/utils/adt/network.c    | 399 +++++++++++++++++++++++++++++++++++++
src/include/catalog/pg_amproc.dat  |   3 +
src/include/catalog/pg_proc.dat    |   3 +
src/test/regress/expected/inet.out | 189 ++++++++++++++++++
src/test/regress/sql/inet.sql      |  95 +++++++++
5 files changed, 689 insertions(+)