pgsql: Rethink original decision to use AND/OR Expr nodes to represent

Log Message:
-----------
Rethink original decision to use AND/OR Expr nodes to represent bitmap
logic operations during planning. Seems cleaner to create two new Path
node types, instead --- this avoids duplication of cost-estimation code.
Also, create an enable_bitmapscan GUC parameter to control use of bitmap
plans.

Modified Files:
--------------
pgsql/doc/src/sgml:
runtime.sgml (r1.313 -> r1.314)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/runtime.sgml.diff?r1=1.313&r2=1.314)
pgsql/src/backend/nodes:
outfuncs.c (r1.248 -> r1.249)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/nodes/outfuncs.c.diff?r1=1.248&r2=1.249)
pgsql/src/backend/optimizer:
README (r1.30 -> r1.31)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/README.diff?r1=1.30&r2=1.31)
pgsql/src/backend/optimizer/path:
allpaths.c (r1.126 -> r1.127)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/path/allpaths.c.diff?r1=1.126&r2=1.127)
costsize.c (r1.143 -> r1.144)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/path/costsize.c.diff?r1=1.143&r2=1.144)
pgsql/src/backend/optimizer/plan:
createplan.c (r1.181 -> r1.182)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/plan/createplan.c.diff?r1=1.181&r2=1.182)
pgsql/src/backend/optimizer/util:
pathnode.c (r1.117 -> r1.118)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/util/pathnode.c.diff?r1=1.117&r2=1.118)
pgsql/src/backend/tcop:
postgres.c (r1.442 -> r1.443)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/tcop/postgres.c.diff?r1=1.442&r2=1.443)
pgsql/src/backend/utils/misc:
guc.c (r1.259 -> r1.260)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/guc.c.diff?r1=1.259&r2=1.260)
postgresql.conf.sample (r1.139 -> r1.140)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/postgresql.conf.sample.diff?r1=1.139&r2=1.140)
pgsql/src/bin/psql:
tab-complete.c (r1.124 -> r1.125)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/psql/tab-complete.c.diff?r1=1.124&r2=1.125)
pgsql/src/include/nodes:
nodes.h (r1.167 -> r1.168)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/nodes/nodes.h.diff?r1=1.167&r2=1.168)
relation.h (r1.106 -> r1.107)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/nodes/relation.h.diff?r1=1.106&r2=1.107)
pgsql/src/include/optimizer:
cost.h (r1.65 -> r1.66)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/optimizer/cost.h.diff?r1=1.65&r2=1.66)
pathnode.h (r1.58 -> r1.59)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/optimizer/pathnode.h.diff?r1=1.58&r2=1.59)
pgsql/src/test/regress/expected:
rangefuncs.out (r1.10 -> r1.11)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/rangefuncs.out.diff?r1=1.10&r2=1.11)