Array initialisation notation in syscache.c

Hi,

While hacking on a new system catalogue for a nearby thread, it
occurred to me that syscache.c's table of entries could be made more
readable and less error prone. They look like this:

{AttributeRelationId, /* ATTNUM */
AttributeRelidNumIndexId,
2,
{
Anum_pg_attribute_attrelid,
Anum_pg_attribute_attnum,
0,
0
},
128
},

Do you think this is better?

[ATTNUM] = {
AttributeRelationId,
AttributeRelidNumIndexId,
{
Anum_pg_attribute_attrelid,
Anum_pg_attribute_attnum
},
128
},

We could also consider writing eg ".nbuckets = 128", but it's not a
complicated struct that the eye gets lost in, so I didn't bother with
that in the attached.