pgsql: Redefine the lp_flags field of item pointers as having four

Log Message:
-----------
Redefine the lp_flags field of item pointers as having four states, rather
than two independent bits (one of which was never used in heap pages anyway,
or at least hadn't been in a very long time). This gives us flexibility to
add the HOT notions of redirected and dead item pointers without requiring
anything so klugy as magic values of lp_off and lp_len. The state values
are chosen so that for the states currently in use (pre-HOT) there is no
change in the physical representation.

Modified Files:
--------------
pgsql/contrib/pageinspect:
btreefuncs.c (r1.4 -> r1.5)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/pageinspect/btreefuncs.c?r1=1.4&r2=1.5)
heapfuncs.c (r1.1 -> r1.2)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/pageinspect/heapfuncs.c?r1=1.1&r2=1.2)
pgsql/contrib/pgstattuple:
pgstattuple.c (r1.28 -> r1.29)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/pgstattuple/pgstattuple.c?r1=1.28&r2=1.29)
pgsql/src/backend/access/gin:
ginentrypage.c (r1.7 -> r1.8)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/gin/ginentrypage.c?r1=1.7&r2=1.8)
ginvacuum.c (r1.15 -> r1.16)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/gin/ginvacuum.c?r1=1.15&r2=1.16)
ginxlog.c (r1.7 -> r1.8)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/gin/ginxlog.c?r1=1.7&r2=1.8)
pgsql/src/backend/access/gist:
gist.c (r1.145 -> r1.146)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/gist/gist.c?r1=1.145&r2=1.146)
gistget.c (r1.66 -> r1.67)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/gist/gistget.c?r1=1.66&r2=1.67)
gistutil.c (r1.22 -> r1.23)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/gist/gistutil.c?r1=1.22&r2=1.23)
gistvacuum.c (r1.30 -> r1.31)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/gist/gistvacuum.c?r1=1.30&r2=1.31)
pgsql/src/backend/access/hash:
hash.c (r1.95 -> r1.96)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/hash/hash.c?r1=1.95&r2=1.96)
hashinsert.c (r1.45 -> r1.46)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/hash/hashinsert.c?r1=1.45&r2=1.46)
hashovfl.c (r1.58 -> r1.59)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/hash/hashovfl.c?r1=1.58&r2=1.59)
hashpage.c (r1.68 -> r1.69)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/hash/hashpage.c?r1=1.68&r2=1.69)
pgsql/src/backend/access/heap:
heapam.c (r1.239 -> r1.240)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/heap/heapam.c?r1=1.239&r2=1.240)
hio.c (r1.65 -> r1.66)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/heap/hio.c?r1=1.65&r2=1.66)
rewriteheap.c (r1.5 -> r1.6)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/heap/rewriteheap.c?r1=1.5&r2=1.6)
pgsql/src/backend/access/nbtree:
README (r1.17 -> r1.18)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/nbtree/README?r1=1.17&r2=1.18)
nbtinsert.c (r1.158 -> r1.159)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/nbtree/nbtinsert.c?r1=1.158&r2=1.159)
nbtpage.c (r1.102 -> r1.103)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/nbtree/nbtpage.c?r1=1.102&r2=1.103)
nbtsort.c (r1.111 -> r1.112)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/nbtree/nbtsort.c?r1=1.111&r2=1.112)
nbtutils.c (r1.85 -> r1.86)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/nbtree/nbtutils.c?r1=1.85&r2=1.86)
nbtxlog.c (r1.44 -> r1.45)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/nbtree/nbtxlog.c?r1=1.44&r2=1.45)
pgsql/src/backend/commands:
sequence.c (r1.144 -> r1.145)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/sequence.c?r1=1.144&r2=1.145)
trigger.c (r1.218 -> r1.219)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/trigger.c?r1=1.218&r2=1.219)
vacuum.c (r1.357 -> r1.358)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/vacuum.c?r1=1.357&r2=1.358)
vacuumlazy.c (r1.94 -> r1.95)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/vacuumlazy.c?r1=1.94&r2=1.95)
pgsql/src/backend/executor:
nodeBitmapHeapscan.c (r1.18 -> r1.19)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/nodeBitmapHeapscan.c?r1=1.18&r2=1.19)
pgsql/src/backend/storage/page:
bufpage.c (r1.72 -> r1.73)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/page/bufpage.c?r1=1.72&r2=1.73)
pgsql/src/include/storage:
bufpage.h (r1.72 -> r1.73)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/storage/bufpage.h?r1=1.72&r2=1.73)
itemid.h (r1.27 -> r1.28)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/storage/itemid.h?r1=1.27&r2=1.28)