pgsql: Arrange for the postmaster (and standalone backends, initdb, etc)

Log Message:
-----------
Arrange for the postmaster (and standalone backends, initdb, etc) to
chdir into PGDATA and subsequently use relative paths instead of absolute
paths to access all files under PGDATA.  This seems to give a small
performance improvement, and it should make the system more robust
against naive DBAs doing things like moving a database directory that
has a live postmaster in it.  Per recent discussion.

Modified Files:
--------------
    pgsql/contrib/dbsize:
        dbsize.c (r1.18 -> r1.19)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/dbsize/dbsize.c.diff?r1=1.18&r2=1.19)
    pgsql/src/backend/access/transam:
        slru.c (r1.25 -> r1.26)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/transam/slru.c.diff?r1=1.25&r2=1.26)
        twophase.c (r1.7 -> r1.8)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/transam/twophase.c.diff?r1=1.7&r2=1.8)
        xlog.c (r1.205 -> r1.206)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/transam/xlog.c.diff?r1=1.205&r2=1.206)
    pgsql/src/backend/bootstrap:
        bootstrap.c (r1.204 -> r1.205)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/bootstrap/bootstrap.c.diff?r1=1.204&r2=1.205)
    pgsql/src/backend/catalog:
        catalog.c (r1.61 -> r1.62)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/catalog.c.diff?r1=1.61&r2=1.62)
    pgsql/src/backend/commands:
        tablespace.c (r1.23 -> r1.24)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/tablespace.c.diff?r1=1.23&r2=1.24)
    pgsql/src/backend/libpq:
        be-secure.c (r1.57 -> r1.58)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/libpq/be-secure.c.diff?r1=1.57&r2=1.58)
    pgsql/src/backend/postmaster:
        pgarch.c (r1.16 -> r1.17)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/pgarch.c.diff?r1=1.16&r2=1.17)
        pgstat.c (r1.98 -> r1.99)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/pgstat.c.diff?r1=1.98&r2=1.99)
        postmaster.c (r1.457 -> r1.458)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/postmaster.c.diff?r1=1.457&r2=1.458)
        syslogger.c (r1.15 -> r1.16)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/syslogger.c.diff?r1=1.15&r2=1.16)
    pgsql/src/backend/storage/file:
        fd.c (r1.117 -> r1.118)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/file/fd.c.diff?r1=1.117&r2=1.118)
    pgsql/src/backend/storage/freespace:
        freespace.c (r1.45 -> r1.46)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/freespace/freespace.c.diff?r1=1.45&r2=1.46)
    pgsql/src/backend/storage/smgr:
        md.c (r1.116 -> r1.117)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/smgr/md.c.diff?r1=1.116&r2=1.117)
    pgsql/src/backend/tcop:
        postgres.c (r1.451 -> r1.452)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/tcop/postgres.c.diff?r1=1.451&r2=1.452)
    pgsql/src/backend/utils/adt:
        misc.c (r1.44 -> r1.45)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/misc.c.diff?r1=1.44&r2=1.45)
    pgsql/src/backend/utils/init:
        flatfiles.c (r1.11 -> r1.12)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/init/flatfiles.c.diff?r1=1.11&r2=1.12)
        globals.c (r1.95 -> r1.96)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/init/globals.c.diff?r1=1.95&r2=1.96)
        miscinit.c (r1.144 -> r1.145)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/init/miscinit.c.diff?r1=1.144&r2=1.145)
        postinit.c (r1.151 -> r1.152)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/init/postinit.c.diff?r1=1.151&r2=1.152)
    pgsql/src/backend/utils/misc:
        guc.c (r1.271 -> r1.272)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/guc.c.diff?r1=1.271&r2=1.272)
    pgsql/src/bin/pg_resetxlog:
        pg_resetxlog.c (r1.34 -> r1.35)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_resetxlog/pg_resetxlog.c.diff?r1=1.34&r2=1.35)
    pgsql/src/include/access:
        slru.h (r1.11 -> r1.12)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/access/slru.h.diff?r1=1.11&r2=1.12)
        xlog.h (r1.65 -> r1.66)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/access/xlog.h.diff?r1=1.65&r2=1.66)
        xlog_internal.h (r1.8 -> r1.9)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/access/xlog_internal.h.diff?r1=1.8&r2=1.9)
    pgsql/src/include:
        miscadmin.h (r1.176 -> r1.177)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/miscadmin.h.diff?r1=1.176&r2=1.177)