pgsql: Give a more user-friendly error message in case where a table is

Log Message:
-----------
Give a more user-friendly error message in case where a table is created
in a schema whose default tablespace has been dropped.

Modified Files:
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pgsql/src/backend/commands:
tablecmds.c (r1.134 -> r1.135)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/tablecmds.c.diff?r1=1.134&r2=1.135)