Make DatumGetInetP() unpack inet datums with a 1-byte header, and add

a new macro, DatumGetInetPP(), that does not. This brings these macros
in line with other DatumGet*P() macros.

Backpatch to 8.3, where 1-byte header varlenas were introduced.

src/backend/utils/adt/network.c

@@ -907,7 +907,7 @@ convert_network_to_scalar(Datum value, Oid typid)
 		case INETOID:
 		case CIDROID:
 			{
-				inet	   *ip = DatumGetInetP(value);
+				inet	   *ip = DatumGetInetPP(value);
 				int			len;
 				double		res;
 				int			i;

src/include/utils/inet.h

@@ -70,9 +70,11 @@ typedef struct macaddr
 /*
  * fmgr interface macros
  */
-#define DatumGetInetP(X)	((inet *) PG_DETOAST_DATUM_PACKED(X))
+#define DatumGetInetP(X)	((inet *) PG_DETOAST_DATUM(X))
+#define DatumGetInetPP(X)	((inet *) PG_DETOAST_DATUM_PACKED(X))
 #define InetPGetDatum(X)	PointerGetDatum(X)
 #define PG_GETARG_INET_P(n) DatumGetInetP(PG_GETARG_DATUM(n))
+#define PG_GETARG_INET_PP(n) DatumGetInetP(PG_GETARG_DATUM_PACKED(n))
 #define PG_RETURN_INET_P(x) return InetPGetDatum(x)
 /* macaddr is a fixed-length pass-by-reference datatype */
 #define DatumGetMacaddrP(X)    ((macaddr *) DatumGetPointer(X))