Don't print address of ETNode. Print the DFSNumIn which uniquely identifies

Don't print address of ETNode. Print the DFSNumIn which uniquely identifies
the basic block and is stable across runs in gdb or valgrind.

Make Node::update handle edges which dominate and are tighter than
existing edges.

Replace makeEqual's "squeeze theorem" code. Fixes miscompilation.

Gate the calls to defToOps and opsToDef. Before this, we were getting IG
edges about values which weren't even defined in the dominated area. This
reduces the size of the IG by about half.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@33236 91177308-0d34-0410-b5e6-96231b3b80d8