xblk.t test failure depending on charset; patch to bloat the test some more

When building DBD::Sybase 1.05 on 'Red Hat Enterprise Linux 3' the
xblk.t test failed because of differing charsets between server and
client.  This can be fixed by setting LC_ALL=C but I don't know if that
should be done in the test code.

Anyway, currently xblk.t makes a temp table with eight columns.  The
identity stuff and other things may work even if character columns
don't.  So I thought it would be a good idea to make xblk.t run the
tests eight times, first with just the first column, then with the first
and second columns, and so on.  The attached patch does that.  It is
cumulative on the patch I sent yesterday.

I'd be interested to hear your views on how to fix the charset issue
so the test suite runs smoothly or gives a more helpful error.

-- 
Ed Avis <[email protected]>