BasicConstraintManager:

BasicConstraintManager:
- Fix nonsensical logic in AssumeSymLE. When comparing 'sym <= constant' and the
  constant is the minimum integer value, add the constraint that 'sym ==
  constant' when the path is deemed feasible.  All other cases are feasible.
- Improve AssumeSymLT to address <rdar://problem/6407949>.  When comparing
  'sym < constant' and constant is the minimum integer value we know the
  path is infeasible.
- Add test case for <rdar://problem/6407949>.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@60489 91177308-0d34-0410-b5e6-96231b3b80d8