pgsql: Adjust permissions checking for ALTER OWNER commands: instead of

Log Message:
-----------
Adjust permissions checking for ALTER OWNER commands: instead of
requiring superuserness always, allow an owner to reassign ownership
to any role he is a member of, if that role would have the right to
create a similar object.  These three requirements essentially state
that the would-be alterer has enough privilege to DROP the existing
object and then re-CREATE it as the new role; so we might as well
let him do it in one step.  The ALTER TABLESPACE case is a bit
squirrely, but the whole concept of non-superuser tablespace owners
is pretty dubious anyway.  Stephen Frost, code review by Tom Lane.

Modified Files:
--------------
    pgsql/src/backend/commands:
        aggregatecmds.c (r1.27 -> r1.28)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/aggregatecmds.c.diff?r1=1.27&r2=1.28)
        conversioncmds.c (r1.20 -> r1.21)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/conversioncmds.c.diff?r1=1.20&r2=1.21)
        dbcommands.c (r1.166 -> r1.167)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/dbcommands.c.diff?r1=1.166&r2=1.167)
        functioncmds.c (r1.63 -> r1.64)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/functioncmds.c.diff?r1=1.63&r2=1.64)
        opclasscmds.c (r1.34 -> r1.35)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/opclasscmds.c.diff?r1=1.34&r2=1.35)
        operatorcmds.c (r1.23 -> r1.24)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/operatorcmds.c.diff?r1=1.23&r2=1.24)
        schemacmds.c (r1.32 -> r1.33)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/schemacmds.c.diff?r1=1.32&r2=1.33)
        tablecmds.c (r1.163 -> r1.164)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/tablecmds.c.diff?r1=1.163&r2=1.164)
        tablespace.c (r1.25 -> r1.26)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/tablespace.c.diff?r1=1.25&r2=1.26)
        typecmds.c (r1.75 -> r1.76)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/typecmds.c.diff?r1=1.75&r2=1.76)
    pgsql/src/backend/utils/adt:
        acl.c (r1.118 -> r1.119)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/acl.c.diff?r1=1.118&r2=1.119)
    pgsql/src/include/utils:
        acl.h (r1.81 -> r1.82)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/acl.h.diff?r1=1.81&r2=1.82)