split dom frontier handling stuff out to its own DominanceFrontier header,

so that Dominators.h is *just* domtree.  Also prune #includes a bit.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122714 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Analysis/LiveValues.cpp

@@ -13,6 +13,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Analysis/LiveValues.h"
+#include "llvm/Instructions.h"
 #include "llvm/Analysis/Dominators.h"
 #include "llvm/Analysis/LoopInfo.h"
 using namespace llvm;