add a new AST generator test case

add a new AST generator test case

Older versions of isl would produce the following output
for this test case:

    for (int c0 = 2; c0 <= 200; c0 += 64) {
      if (c0 <= 66)
	for (int c2 = c0 - 1; c2 <= 120; c2 += 1)
	  s2(c0, c2);
      if (c0 >= 66)
	for (int c2 = 122; c2 <= c0 + 62; c2 += 1)
	  s4(c0, c2);
    }

The constraint c0 <= 66 is redundant with respect to c0 - 1 <= 120,
i.e., c0 <= 121 and the fact that c0 is equal to a multiple of
64 plus 2.

After the reorganization in the previous commit, these extra
constraints are no longer being generated.

Reported-by: Tobias Grosser <tobias@grosser.es>
Signed-off-by: Sven Verdoolaege <skimo@kotnet.org>