pgsql: Back out fix for Unicode characters above 0x10000

Log Message:
-----------
Back out fix for Unicode characters above 0x10000

Modified Files:
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pgsql/doc/src/sgml:
postgres.sgml (r1.65 -> r1.66)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/postgres.sgml.diff?r1=1.65&r2=1.66)
pgsql/src/backend/utils/mb:
wchar.c (r1.39 -> r1.40)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/mb/wchar.c.diff?r1=1.39&r2=1.40)
pgsql/src/include/mb:
pg_wchar.h (r1.54 -> r1.55)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/mb/pg_wchar.h.diff?r1=1.54&r2=1.55)