pgsql-server: Get rid of the former rather baroque mechanism for

Log Message:
-----------
Get rid of the former rather baroque mechanism for propagating the values
of ThisStartUpID and RedoRecPtr into new backends. It's a lot easier just
to make them all grab the values out of shared memory during startup.
This helps to decouple the postmaster from checkpoint execution, which I
need since I'm intending to let the bgwriter do it instead, and it also
fixes a bug in the Win32 port: ThisStartUpID wasn't getting propagated at
all AFAICS. (Doesn't give me a lot of faith in the amount of testing that
port has gotten.)

Modified Files:
--------------
pgsql-server/src/backend/access/heap:
heapam.c (r1.167 -> r1.168)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/access/heap/heapam.c.diff?r1=1.167&r2=1.168)
pgsql-server/src/backend/access/transam:
xlog.c (r1.142 -> r1.143)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/access/transam/xlog.c.diff?r1=1.142&r2=1.143)
pgsql-server/src/backend/bootstrap:
bootstrap.c (r1.179 -> r1.180)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/bootstrap/bootstrap.c.diff?r1=1.179&r2=1.180)
pgsql-server/src/backend/postmaster:
postmaster.c (r1.396 -> r1.397)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/postmaster/postmaster.c.diff?r1=1.396&r2=1.397)
pgsql-server/src/backend/utils/init:
postinit.c (r1.131 -> r1.132)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/utils/init/postinit.c.diff?r1=1.131&r2=1.132)
pgsql-server/src/include/access:
xlog.h (r1.49 -> r1.50)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/include/access/xlog.h.diff?r1=1.49&r2=1.50)