Convert a bunch of loops to foreach.  NFC.

After r244074, we now have a successors() method to iterate over
all the successors of a TerminatorInst.  This commit changes a bunch
of eligible loops to use it.

llvm-svn: 244260
diff --git a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
index 1bf92e3..d59eef3 100644
--- a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
+++ b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
@@ -41,8 +41,8 @@
 
   // Loop through all of our successors and make sure they know that one
   // of their predecessors is going away.
-  for (unsigned i = 0, e = BBTerm->getNumSuccessors(); i != e; ++i)
-    BBTerm->getSuccessor(i)->removePredecessor(BB);
+  for (BasicBlock *Succ : BBTerm->successors())
+    Succ->removePredecessor(BB);
 
   // Zap all the instructions in the block.
   while (!BB->empty()) {