While testing particular algorithms to compute loop iteration count the brute

force evaluation (ComputeIterationCountExhaustively) should be turned off.

It doesn't apply to trip-count2.ll because this file tests the brute force
evaluation.

The test for PR2364 (2008-05-25-NegativeStepToZero.ll) currently fails
showing that the patch for this bug doesn't work. I'll fix it in a few hours
with a patch for PR2088.

llvm-svn: 53792