pgsql: Revert the behavior of inet/cidr functions to not unpack the arg

Revert the behavior of inet/cidr functions to not unpack the arguments.

I forgot to change the functions to use the PG_GETARG_INET_PP() macro,
when I changed DatumGetInetP() to unpack the datum, like Datum*P macros
usually do. Also, I screwed up the definition of the PG_GETARG_INET_PP()
macro, and didn't notice because it wasn't used.

This fixes the memory leak when sorting inet values, as reported
by Jochen Erwied and debugged by Andres Freund. Backpatch to 8.3, like
the previous patch that broke it.

Branch
------
REL9_1_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/6cf639dfbddbc44d027730ad1504886312bc905a

Modified Files
--------------
src/backend/utils/adt/network.c |   98 +++++++++++++++++++-------------------
src/include/utils/inet.h        |    2 +-
2 files changed, 50 insertions(+), 50 deletions(-)