t8005: use more portable character encoding names

t8005: use more portable character encoding names

Some platforms do not have an extensive list of alternate names for
character encodings.

Solaris 7 does not know about shift-jis, but does know SJIS.  It also does
not know that utf-8 and UTF-8 refer to the same encoding.

With the above in mind, the following conversions were performed:

      utf-8 --> UTF-8
  shift-jis --> SJIS

Signed-off-by: Brandon Casey <casey@nrlssc.navy.mil>
Signed-off-by: Junio C Hamano <gitster@pobox.com>