reorder ALLOW_TEXTCONV option setting

reorder ALLOW_TEXTCONV option setting

Right now for the diff porcelain and the log family, we
call:

  init_revisions();
  setup_revisions();
  DIFF_OPT_SET(ALLOW_TEXTCONV);

However, that means textconv will _always_ be on, instead of
being a default that can be manipulated with
setup_revisions. Instead, we want:

  init_revisions();
  DIFF_OPT_SET(ALLOW_TEXTCONV);
  setup_revisions();

which is what this patch does.

We'll go ahead and move the callsite in wt-status, also;
even though the user can't pass any options here, it is a
cleanup that will help avoid any surprise later if the
setup_revisions line is changed.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>