pgsql: Move the responsibility of writing a "unlogged WAL operation"

Log Message:
-----------
Move the responsibility of writing a "unlogged WAL operation" record from
heap_sync() to the callers, because heap_sync() is sometimes called even
if the operation itself is WAL-logged. This eliminates the bogus unlogged
records from CLUSTER that Simon Riggs reported, patch by Fujii Masao.

Modified Files:
--------------
pgsql/src/backend/access/heap:
heapam.c (r1.284 -> r1.285)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/heap/heapam.c?r1=1.284&r2=1.285)
rewriteheap.c (r1.19 -> r1.20)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/heap/rewriteheap.c?r1=1.19&r2=1.20)
pgsql/src/backend/commands:
copy.c (r1.322 -> r1.323)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/copy.c?r1=1.322&r2=1.323)
tablecmds.c (r1.322 -> r1.323)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/tablecmds.c?r1=1.322&r2=1.323)
pgsql/src/backend/executor:
execMain.c (r1.343 -> r1.344)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/execMain.c?r1=1.343&r2=1.344)