pgsql: Add the ability to create indexes 'concurrently', that is,

Log Message:
-----------
Add the ability to create indexes 'concurrently', that is, without
blocking concurrent writes to the table.  Greg Stark, with a little help
from Tom Lane.

Modified Files:
--------------
    pgsql/doc/src/sgml:
        catalogs.sgml (r2.129 -> r2.130)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/catalogs.sgml.diff?r1=2.129&r2=2.130)
        indexam.sgml (r2.16 -> r2.17)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/indexam.sgml.diff?r1=2.16&r2=2.17)
        indices.sgml (r1.57 -> r1.58)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/indices.sgml.diff?r1=1.57&r2=1.58)
        mvcc.sgml (r2.56 -> r2.57)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/mvcc.sgml.diff?r1=2.56&r2=2.57)
    pgsql/doc/src/sgml/ref:
        create_index.sgml (r1.55 -> r1.56)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/create_index.sgml.diff?r1=1.55&r2=1.56)
        reindex.sgml (r1.31 -> r1.32)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/reindex.sgml.diff?r1=1.31&r2=1.32)
    pgsql/src/backend/access/nbtree:
        nbtinsert.c (r1.142 -> r1.143)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/nbtree/nbtinsert.c.diff?r1=1.142&r2=1.143)
    pgsql/src/backend/bootstrap:
        bootparse.y (r1.83 -> r1.84)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/bootstrap/bootparse.y.diff?r1=1.83&r2=1.84)
    pgsql/src/backend/catalog:
        index.c (r1.272 -> r1.273)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/index.c.diff?r1=1.272&r2=1.273)
        toasting.c (r1.1 -> r1.2)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/toasting.c.diff?r1=1.1&r2=1.2)
    pgsql/src/backend/commands:
        indexcmds.c (r1.146 -> r1.147)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/indexcmds.c.diff?r1=1.146&r2=1.147)
        tablecmds.c (r1.200 -> r1.201)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/tablecmds.c.diff?r1=1.200&r2=1.201)
    pgsql/src/backend/nodes:
        copyfuncs.c (r1.348 -> r1.349)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/nodes/copyfuncs.c.diff?r1=1.348&r2=1.349)
        equalfuncs.c (r1.282 -> r1.283)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/nodes/equalfuncs.c.diff?r1=1.282&r2=1.283)
        outfuncs.c (r1.283 -> r1.284)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/nodes/outfuncs.c.diff?r1=1.283&r2=1.284)
    pgsql/src/backend/optimizer/util:
        plancat.c (r1.124 -> r1.125)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/util/plancat.c.diff?r1=1.124&r2=1.125)
    pgsql/src/backend/parser:
        analyze.c (r1.347 -> r1.348)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/analyze.c.diff?r1=1.347&r2=1.348)
        gram.y (r2.557 -> r2.558)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/gram.y.diff?r1=2.557&r2=2.558)
        keywords.c (r1.175 -> r1.176)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/keywords.c.diff?r1=1.175&r2=1.176)
    pgsql/src/backend/storage/page:
        itemptr.c (r1.17 -> r1.18)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/page/itemptr.c.diff?r1=1.17&r2=1.18)
    pgsql/src/backend/tcop:
        utility.c (r1.266 -> r1.267)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/tcop/utility.c.diff?r1=1.266&r2=1.267)
    pgsql/src/backend/utils/adt:
        tid.c (r1.54 -> r1.55)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/tid.c.diff?r1=1.54&r2=1.55)
    pgsql/src/bin/psql:
        common.c (r1.124 -> r1.125)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/psql/common.c.diff?r1=1.124&r2=1.125)
        describe.c (r1.142 -> r1.143)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/psql/describe.c.diff?r1=1.142&r2=1.143)
    pgsql/src/include/catalog:
        catversion.h (r1.352 -> r1.353)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/catversion.h.diff?r1=1.352&r2=1.353)
        index.h (r1.70 -> r1.71)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/index.h.diff?r1=1.70&r2=1.71)
        pg_attribute.h (r1.123 -> r1.124)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_attribute.h.diff?r1=1.123&r2=1.124)
        pg_index.h (r1.39 -> r1.40)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_index.h.diff?r1=1.39&r2=1.40)
    pgsql/src/include/commands:
        defrem.h (r1.75 -> r1.76)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/commands/defrem.h.diff?r1=1.75&r2=1.76)
    pgsql/src/include/nodes:
        execnodes.h (r1.159 -> r1.160)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/nodes/execnodes.h.diff?r1=1.159&r2=1.160)
        parsenodes.h (r1.324 -> r1.325)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/nodes/parsenodes.h.diff?r1=1.324&r2=1.325)
    pgsql/src/include/storage:
        itemptr.h (r1.28 -> r1.29)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/storage/itemptr.h.diff?r1=1.28&r2=1.29)
    pgsql/src/test/regress/expected:
        create_index.out (r1.20 -> r1.21)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/create_index.out.diff?r1=1.20&r2=1.21)
    pgsql/src/test/regress/sql:
        create_index.sql (r1.19 -> r1.20)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/create_index.sql.diff?r1=1.19&r2=1.20)