Cache invalidation was changed a little

Hi

I have just committed changes to cache invalidation stuff.
Maybe this would fix the following TODO.
* elog() flushes cache, try invalidating just entries from current xact,
perhaps using invalidation cache

1) In case of abort,catalog cache and relation cache will
be invalidated for system tuples marked by Relation-
Mark4RollbackHeapTuple(). Both heap_insert() and
heap_update() call RelationMark4RollbackHeapTuple().

2) CommandCounterIncrement() calls AtCommit_LocalCache()
instead of AtCommit_Cache(). Registration of cache
invalidation for other backends was postponed until commit.

3) The new function ImmediateSharedRelationCacheInvalidate()
is called from smgrunlink()/smgrtruncate() in order to register
relation cache invalidation immediately.

Regards.

Hiroshi Inoue
Inoue(at)tpf(dot)co(dot)jp