[plt-scheme] srfi-78 breakage

On Mar 17, Dimitris Vyzovitis wrote:
> The binding of => has broken the srfi-78 check macro:
> (require srfi/78)
> (check 'foo => 'bar)
> stdin::68: check: bad syntax in: (check (quote foo) => (quote bar))

I've switched the implementation from `mzscheme' to `scheme/base'
which solves the problem.  Will be committed soon.

-- 
          ((lambda (x) (x x)) (lambda (x) (x x)))          Eli Barzilay:
                  http://www.barzilay.org/                 Maze is Life!