Rewrite instsimplify's handling if icmp on pointer values to remove the
remaining use of AliasAnalysis concepts such as isIdentifiedObject to
prove pointer inequality.

@external_compare in test/Transforms/InstSimplify/compare.ll shows a simple
case where a noalias argument can be equal to a global variable address, and
while AliasAnalysis can get away with saying that these pointers don't alias,
instsimplify cannot say that they are not equal.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174122 91177308-0d34-0410-b5e6-96231b3b80d8