Revise sinval code to remove no-longer-used tuple TID from inval messages.

This requires adjusting the API for syscache callback functions: they now
get a hash value, not a TID, to identify the target tuple.  Most of them
weren't paying any attention to that argument anyway, but plancache did
require a small amount of fixing.

Also, improve performance a trifle by avoiding sending duplicate inval
messages when a heap_update isn't changing the catcache lookup columns.

src/backend/utils/cache/spccache.c

@@ -50,7 +50,7 @@ typedef struct
  * tablespaces, nor do we expect them to be frequently modified.
  */
 static void
-InvalidateTableSpaceCacheCallback(Datum arg, int cacheid, ItemPointer tuplePtr)
+InvalidateTableSpaceCacheCallback(Datum arg, int cacheid, uint32 hashvalue)
 {
 	HASH_SEQ_STATUS status;
 	TableSpaceCacheEntry *spc;