* Add capability to recognize alias properties of the following common cases:

  - A[c1] cannot alias A[c2] where constants c1 != c2
  - A[i] cannot alias B[j] if A & B are provably different arrays

This should help out array based codes.  For example, from bzip2 from spec,
3 additional loads can be GCSE'd, and _21_ additional loads can be LICMd due
to this change.

In a test example from the Spec GAP benchmark (vecffe.c), this change allows
_52_ additional loads to be GCSE'd and _224_ additional LICM'd loads.

Not bad for such a simple change.  Other testcases show no change at all
because they just don't use arrays.  Not too suprising there.

llvm-svn: 3616