This is a substantial rewrite of the AliasSetTracker class which now uses

This is a substantial rewrite of the AliasSetTracker class which now uses
a union-find based algorithm, is significantly faster, and is more general.
It will also scale to handle call instructions correctly, which is a nice
added bonus.

This includes a new pass -print-alias-sets which can be used to show how
alias sets are formed for a particular analysis.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@5619 91177308-0d34-0410-b5e6-96231b3b80d8