pgsql: Adjust scan plan nodes to avoid getting an extra AccessShareLock

Log Message:
-----------
Adjust scan plan nodes to avoid getting an extra AccessShareLock on a
relation if it's already been locked by execMain.c as either a result
relation or a FOR UPDATE/SHARE relation. This avoids an extra trip to
the shared lock manager state. Per my suggestion yesterday.

Modified Files:
--------------
pgsql/src/backend/executor:
execMain.c (r1.261 -> r1.262)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/execMain.c.diff?r1=1.261&r2=1.262)
execUtils.c (r1.129 -> r1.130)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/execUtils.c.diff?r1=1.129&r2=1.130)
nodeBitmapHeapscan.c (r1.7 -> r1.8)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/nodeBitmapHeapscan.c.diff?r1=1.7&r2=1.8)
nodeBitmapIndexscan.c (r1.12 -> r1.13)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/nodeBitmapIndexscan.c.diff?r1=1.12&r2=1.13)
nodeIndexscan.c (r1.107 -> r1.108)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/nodeIndexscan.c.diff?r1=1.107&r2=1.108)
nodeSeqscan.c (r1.55 -> r1.56)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/nodeSeqscan.c.diff?r1=1.55&r2=1.56)
nodeTidscan.c (r1.45 -> r1.46)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/nodeTidscan.c.diff?r1=1.45&r2=1.46)
pgsql/src/include/executor:
executor.h (r1.121 -> r1.122)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/executor/executor.h.diff?r1=1.121&r2=1.122)
pgsql/src/include/nodes:
execnodes.h (r1.145 -> r1.146)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/nodes/execnodes.h.diff?r1=1.145&r2=1.146)