pgsql: Finish up the flat-files project: get rid of GetRawDatabaseInfo()

Log Message:
-----------
Finish up the flat-files project: get rid of GetRawDatabaseInfo() hack
in favor of looking at the flat file copy of pg_database during backend
startup.  This should finally eliminate the various corner cases in which
backend startup fails unexpectedly because it isn't able to distinguish
live and dead tuples in pg_database.  Simplify locking on pg_database
to be similar to the rules used with pg_shadow and pg_group, and eliminate
FlushRelationBuffers operations that were used only to reduce the odds
of failure of GetRawDatabaseInfo.
initdb forced due to addition of a trigger to pg_database.

Modified Files:
--------------
    pgsql/src/backend/commands:
        dbcommands.c (r1.150 -> r1.151)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/dbcommands.c.diff?r1=1.150&r2=1.151)
        vacuum.c (r1.301 -> r1.302)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/vacuum.c.diff?r1=1.301&r2=1.302)
    pgsql/src/backend/libpq:
        hba.c (r1.139 -> r1.140)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/libpq/hba.c.diff?r1=1.139&r2=1.140)
    pgsql/src/backend/utils/init:
        flatfiles.c (r1.3 -> r1.4)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/init/flatfiles.c.diff?r1=1.3&r2=1.4)
        postinit.c (r1.140 -> r1.141)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/init/postinit.c.diff?r1=1.140&r2=1.141)
    pgsql/src/backend/utils/misc:
        Makefile (r1.22 -> r1.23)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/Makefile.diff?r1=1.22&r2=1.23)
    pgsql/src/bin/initdb:
        initdb.c (r1.75 -> r1.76)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/initdb/initdb.c.diff?r1=1.75&r2=1.76)
    pgsql/src/include/catalog:
        catversion.h (r1.254 -> r1.255)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/catversion.h.diff?r1=1.254&r2=1.255)
        pg_proc.h (r1.349 -> r1.350)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_proc.h.diff?r1=1.349&r2=1.350)
    pgsql/src/include/libpq:
        hba.h (r1.35 -> r1.36)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/libpq/hba.h.diff?r1=1.35&r2=1.36)
    pgsql/src/include:
        miscadmin.h (r1.174 -> r1.175)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/miscadmin.h.diff?r1=1.174&r2=1.175)

Removed Files:
-------------
    pgsql/src/backend/utils/misc:
        database.c
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/database.c)