pgsql: Ignore UTF-8-encoded Unicode byte-order mark at the beginning of

Log Message:
-----------
Ignore UTF-8-encoded Unicode byte-order mark at the beginning of a file if
the client encoding is UTF-8.

a limited version of a patch proposed by Itagaki Takahiro

Modified Files:
--------------
pgsql/src/bin/psql:
mainloop.c (r1.96 -> r1.97)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/psql/mainloop.c?r1=1.96&r2=1.97)