pgsql: Clean up API for ambulkdelete/amvacuumcleanup as per today's

Log Message:
-----------
Clean up API for ambulkdelete/amvacuumcleanup as per today's discussion.
This formulation requires every AM to provide amvacuumcleanup, unlike before,
but it's surely a whole lot cleaner. Also, add an 'amstorage' column to
pg_am so that we can get rid of hardwired knowledge in DefineOpClass().

Modified Files:
--------------
pgsql/doc/src/sgml:
catalogs.sgml (r2.121 -> r2.122)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/catalogs.sgml.diff?r1=2.121&r2=2.122)
indexam.sgml (r2.9 -> r2.10)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/indexam.sgml.diff?r1=2.9&r2=2.10)
pgsql/src/backend/access/gin:
ginvacuum.c (r1.1 -> r1.2)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/gin/ginvacuum.c.diff?r1=1.1&r2=1.2)
pgsql/src/backend/access/gist:
gistvacuum.c (r1.18 -> r1.19)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/gist/gistvacuum.c.diff?r1=1.18&r2=1.19)
pgsql/src/backend/access/hash:
hash.c (r1.88 -> r1.89)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/hash/hash.c.diff?r1=1.88&r2=1.89)
pgsql/src/backend/access/index:
indexam.c (r1.91 -> r1.92)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/index/indexam.c.diff?r1=1.91&r2=1.92)
pgsql/src/backend/access/nbtree:
nbtree.c (r1.145 -> r1.146)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/nbtree/nbtree.c.diff?r1=1.145&r2=1.146)
pgsql/src/backend/commands:
cluster.c (r1.146 -> r1.147)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/cluster.c.diff?r1=1.146&r2=1.147)
opclasscmds.c (r1.44 -> r1.45)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/opclasscmds.c.diff?r1=1.44&r2=1.45)
vacuum.c (r1.327 -> r1.328)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/vacuum.c.diff?r1=1.327&r2=1.328)
vacuumlazy.c (r1.69 -> r1.70)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/vacuumlazy.c.diff?r1=1.69&r2=1.70)
pgsql/src/include/access:
genam.h (r1.58 -> r1.59)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/access/genam.h.diff?r1=1.58&r2=1.59)
hash.h (r1.68 -> r1.69)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/access/hash.h.diff?r1=1.68&r2=1.69)
pgsql/src/include/catalog:
catversion.h (r1.330 -> r1.331)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/catversion.h.diff?r1=1.330&r2=1.331)
pg_am.h (r1.41 -> r1.42)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_am.h.diff?r1=1.41&r2=1.42)
pg_proc.h (r1.409 -> r1.410)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_proc.h.diff?r1=1.409&r2=1.410)