pgsql-server: Separate out bgwriter code into a logically separate

Log Message:
-----------
Separate out bgwriter code into a logically separate module, rather
than being random pieces of other files.  Give bgwriter responsibility
for all checkpoint activity (other than a post-recovery checkpoint);
so this child process absorbs the functionality of the former transient
checkpoint and shutdown subprocesses.  While at it, create an actual
include file for postmaster.c, which for some reason never had its own
file before.

Modified Files:
--------------
    pgsql-server/src/backend/access/transam:
        slru.c (r1.14 -> r1.15)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/access/transam/slru.c.diff?r1=1.14&r2=1.15)
        xlog.c (r1.144 -> r1.145)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/access/transam/xlog.c.diff?r1=1.144&r2=1.145)
    pgsql-server/src/backend/bootstrap:
        bootstrap.c (r1.181 -> r1.182)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/bootstrap/bootstrap.c.diff?r1=1.181&r2=1.182)
    pgsql-server/src/backend/libpq:
        pqsignal.c (r1.33 -> r1.34)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/libpq/pqsignal.c.diff?r1=1.33&r2=1.34)
    pgsql-server/src/backend/main:
        main.c (r1.84 -> r1.85)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/main/main.c.diff?r1=1.84&r2=1.85)
    pgsql-server/src/backend/postmaster:
        Makefile (r1.14 -> r1.15)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/postmaster/Makefile.diff?r1=1.14&r2=1.15)
        pgstat.c (r1.72 -> r1.73)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/postmaster/pgstat.c.diff?r1=1.72&r2=1.73)
        postmaster.c (r1.399 -> r1.400)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/postmaster/postmaster.c.diff?r1=1.399&r2=1.400)
    pgsql-server/src/backend/storage/buffer:
        bufmgr.c (r1.165 -> r1.166)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/storage/buffer/bufmgr.c.diff?r1=1.165&r2=1.166)
    pgsql-server/src/backend/storage/ipc:
        ipci.c (r1.67 -> r1.68)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/storage/ipc/ipci.c.diff?r1=1.67&r2=1.68)
        pmsignal.c (r1.13 -> r1.14)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/storage/ipc/pmsignal.c.diff?r1=1.13&r2=1.14)
    pgsql-server/src/backend/storage/lmgr:
        proc.c (r1.147 -> r1.148)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/storage/lmgr/proc.c.diff?r1=1.147&r2=1.148)
    pgsql-server/src/backend/tcop:
        postgres.c (r1.416 -> r1.417)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/tcop/postgres.c.diff?r1=1.416&r2=1.417)
        utility.c (r1.217 -> r1.218)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/tcop/utility.c.diff?r1=1.217&r2=1.218)
    pgsql-server/src/backend/utils/error:
        elog.c (r1.138 -> r1.139)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/utils/error/elog.c.diff?r1=1.138&r2=1.139)
    pgsql-server/src/backend/utils/init:
        globals.c (r1.88 -> r1.89)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/utils/init/globals.c.diff?r1=1.88&r2=1.89)
        postinit.c (r1.132 -> r1.133)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/utils/init/postinit.c.diff?r1=1.132&r2=1.133)
    pgsql-server/src/backend/utils/misc:
        guc.c (r1.208 -> r1.209)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/utils/misc/guc.c.diff?r1=1.208&r2=1.209)
    pgsql-server/src/include/access:
        xlog.h (r1.50 -> r1.51)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/include/access/xlog.h.diff?r1=1.50&r2=1.51)
    pgsql-server/src/include/bootstrap:
        bootstrap.h (r1.34 -> r1.35)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/include/bootstrap/bootstrap.h.diff?r1=1.34&r2=1.35)
    pgsql-server/src/include:
        miscadmin.h (r1.161 -> r1.162)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/include/miscadmin.h.diff?r1=1.161&r2=1.162)
        pgstat.h (r1.22 -> r1.23)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/include/pgstat.h.diff?r1=1.22&r2=1.23)
    pgsql-server/src/include/storage:
        bufmgr.h (r1.79 -> r1.80)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/include/storage/bufmgr.h.diff?r1=1.79&r2=1.80)
        pmsignal.h (r1.7 -> r1.8)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/include/storage/pmsignal.h.diff?r1=1.7&r2=1.8)
    pgsql-server/src/include/tcop:
        tcopprot.h (r1.65 -> r1.66)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/include/tcop/tcopprot.h.diff?r1=1.65&r2=1.66)

Added Files:
-----------
    pgsql-server/src/backend/postmaster:
        bgwriter.c (r1.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/postmaster/bgwriter.c?rev=1.1&content-type=text/x-cvsweb-markup)
    pgsql-server/src/include/postmaster:
        bgwriter.h (r1.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/include/postmaster/bgwriter.h?rev=1.1&content-type=text/x-cvsweb-markup)
        postmaster.h (r1.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/include/postmaster/postmaster.h?rev=1.1&content-type=text/x-cvsweb-markup)