[InstCombine] Transform A & (L - 1) u< L --> L != 0

Summary:
This transform is never a pessimization at the IR level (since it
replaces an `icmp` with another), and has potentiall payoffs:

 1. It may make the `icmp` fold away or become loop invariant.
 2. It may make the `A & (L - 1)` computation dead.

This shows up in Java, in range checks generated by array accesses of
the form `a[i & (a.length - 1)]`.

Reviewers: reames, majnemer

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D12210

llvm-svn: 245635